There are lots of great resources available on the Internet for learning more about programming and improving your skills. Blogs are one of the best, IMO. There's a wealth of knowledge and experience, much of it covering topics not often found in traditional books, and the increased community aspect helps to bring in multiple viewpoints and ideas.
We're probably all familiar with Coding Horror  and Joel on Software  (so no need to mention them), but what are the other great ones out there? What are the Blogs that you find yourself following most closely? Where you see the best new ideas, the most interesting or informative ideas, or just the posts that make you sit back and think?
One Blog per answer, and then we'll vote up the best so we can all learn from them.
The Daily WTF  - Helping us learn from our own collective (bone-headed) mistakes. http://thedailywtf.com/
Here's the Top 10 development blogs...
and you can find the rest of the Top 100 Blogs here . http://www.joelonsoftware.com/
Coding Horror  from our own Jeff Attwood :) http://www.codinghorror.com/blog/
Arguably not a blog, but Paul Graham  has a great collection of essays. Of special interest if you are considering to, or already running, a startup.
I'd strongly encourage you to read all essays. http://www.paulgraham.com/
Rands in Repose  http://www.randsinrepose.com/
Lambda The Ultimate  - For the Computer Scientist inside us all ;-) http://lambda-the-ultimate.org/
The blog of Oren Eini (aka Ayende Rahien)  http://www.ayende.com/Blog/
Joel on Software 
(I'm really curious to see it's position among other blogs in the vote.) http://www.joelonsoftware.com
Oh, and you've been haacked  http://haacked.com/
Gustavo Duarte  for low level topics, close to the hardware. http://duartes.org/gustavo/blog/
Nobody's mentioned CodeBetter  yet, so I'll add that one to the list. http://codebetter.com/
I know most of these were mentioned.. but I check them regularly. Most of them are .NET centric
Scott Guthrie 
Scott Hanselman 
Coding Horror 
Carnage4Life  http://weblogs.asp.net/scottgu/
Coding4Fun  http://blogs.msdn.com/coding4fun/default.aspx
Joe Armstrong , mostly covering Erlang. http://armstrongonsoftware.blogspot.com/
He also includes a opml file for easily importing this list into your rss reader.
EDIT: Here's the latest list "Top 100 Blogs for Developers (Q1 2009)"  ... and no surprises that Joel and Jeff are at the top there ;-) http://www.noop.nl/2008/09/top-100-blogs-for-development-managers-q3-2008.html
The google testing blog  is pretty kickass.
Also, I don't think anyone has yet mentioned Martin Fowler's bliki , but it contains a ton of gems from one of the most well respected minds in the industry.
If you're interested at all in scalability, you should watch highscalability.com  http://googletesting.blogspot.com/
http://martinfowler.com/bliki (one item per answer!)
Bruce Schneier  Has an excellent blog on IT security. http://www.schneier.com/blog/
Ted Dziuba 's blog is a very cynical blog about coding and always makes me laugh. He also rants a lot. http://teddziuba.com/
The Berkun Blog  http://www.scottberkun.com/blog/
Just one? Hmm... CSS Tricks , for the web devs. http://css-tricks.com/
I second Artima . I can't vote up yet :) http://www.artima.com
Google Testing Blog  is quite good. http://googletesting.blogspot.com/
The object mentor developers  web blog. Robert C. Martin & co. http://blogs.objectmentor.com
Moserware  - I think I started reading this when it was linked from Coding Horror once. Relatively new blogger but his posts are interesting and well thought out. http://www.moserware.com/
Some of the tech blogs I usually follow are
Stack Overflow - just browsing through the latest questions always opens up new ideas for me.
Hanselminutes  podcast http://www.hanselminutes.com/
.NET Rocks  podcast http://www.dotnetrocks.com
Good look at general software best practices. Object Mentor  http://blog.objectmentor.com/
Dot Net Perls.  http://dotnetperls.com/
Programming Languages Comparison blog...
Tutkiun  http://programminglanguagefaqs.blogspot.com/
Charles Nutter , about JRuby internals. http://blog.headius.com/
Landon Dyer, the Dadhacker  covers mostly low level topics close to the hardware. http://www.dadhacker.com/blog/
Cathy Sierra's ' Creating Passionate Users ' was/is my favourite. http://headrush.typepad.com/
Ajaxian.com  http://ajaxian.com/
The Contrarian Software Blog 
"Because so much conventional wisdom in the software industry is just plain wrong." http://www.contrariansoftware.com/
Joel on Software  : Joel Spolsky
ScottGu's Blog : Scott Guthrie http://www.joelonsoftware.com/
Peter-Paul Koch's blog on quirksmode.org  http://quirksmode.org
Los Techies  http://www.lostechies.com/blogs/
I also read Raganwald . It looks like he doesn't write any more, but you can read the archives and I like the links, too. http://weblog.raganwald.com
Myke's Weblog  http://www.mykesweblog.com/
Ian Bicking's  http://blog.ianbicking.org/
devlicio.us  http://devlicio.us/blogs/
The Fullasagoog aggregator brings together over 500 hand picked blogs, focused on the Adobe technology platform and related topics. If you are interested in Flash, Flex, AIR or ColdFusion this is a fabulous place to start.
It is supposedly for software development managers, but in my opionion they are just as much for developers that are not managers (such as myself). All of my favourite bloggers (for example Jeff Atwood, Joel Spolsky, Steve Yegge, Martin Fowler, Reginald Braithwaite) are on the list. http://www.noop.nl
I like the realtime collision detection blog .
Despite its name it covers way more than collision detection and has a lot of interesting and sometimes provocative ideas on programming in general. http://realtimecollisiondetection.net/blog/
DevelopDotStar : The Independent Magazine for Software Developers. http://www.developerdotstar.com/
I'm rather surprised that no one has mentioned
I don't follow that many blogs, but this one has caught my attention because of the many delightfully well written posts, like this introduction to evolutionary computation  - surprisingly interesting, for me, for such a theoretical subject. I (and my team) also owe it to this blog that I found out about Hudson  a while back; it has later replaced CruiseControl in our use due to its superior ease of configuration.
Personally I consider it a plus that most of the blog's concrete coding related posts are Java specific (along with some Haskell stuff). Even if you disagree with that, you may be interested in the insightful articles on software development in general, such as this one about the importance of sleep , or witty social commentary about online phenomena like the ongoing Twitter experiment . http://blog.uncommons.org/
If you happen to know some Spanish language (and perhaps enjoy learning more of it) and are into web development, and Linux / open source stuff, check out the blog maintained by
 (a Mexican web developer)
Subheading: Desarrollo y Diseño Web : Software Libre : Linux : Web 2.0
Aside from web development and design content, notable (mainly open-source) software releases and sometimes major hardware or tech business news are covered. This is high-quality stuff; I may not know a comparable general tech blog (for my tastes, anyway) in any language. http://gespadas.com/blog/
I'll add my own: Coding Relic . Feel free to vote it down, I'm used to it. http://codingrelic.geekhold.com/
Here's a horrible one.
http://www.stackoverthrow.com/ some rants about development and things.
Disclaimer: I'm the author. Feel free to downvote for shameless plug.
BTW, what happened to Mr. Ed's hacknot.info? It just shows a generic site since months.
I rather enjoy:
and I've gotten some helpful code from Software Evolved . http://www.peterfranza.com
Ryan's Scraps 
Keeps me up to date on the bleeding edge of Ruby on Rails. http://ryandaigle.com/
I didn't see Ode To Code  in this list yet. http://www.odetocode.com/
Even though I don't write any Ruby, I am really missing raganwald  because of the thought provoking posts, the fact that I ended up learning things that would never have come up just reading .NET blogs, and because the links he posted were always worth a read.
Thankfully it looks like he's thinking about starting up a new blog . http://weblog.raganwald.com/2008/05/narcissism-of-small-code-differences.html
Peter Kankowski - who writes smallcode , never ceases to teach me new things. http://smallcode.weblogs.us/
For testing subjects, I've enjoyed James Bach's Blog  although he must have died because he hasn't posted any new entries in a while.
I also like a guy named Shrini Kulikarni . And from either of those blogs, their blogrolls will take you to a number of other good sites. http://www.satisfice.com/blog/
Less known I think:
For all you Erlang'ers out there (it's what the cool kids are doing.)
blog.beerriot.com -- Bryan Fink (one of the guys behind Riak.)
yariv's blog is also a good one.
This guy seems to know his Perl stuff, yet makes his blog entries interesting and readable to non-geeks:
Jorge Dunkelman's blog  may be of interest to Spanish speakers, especially those needing help with Excel. http://jldexcelsp.blogspot.com/
Lastly, here's a useful source on MySQL admin and performance stuff (lots more blogs via Planet MySQL .)
I hope these links are of use to someone out there! http://www.planetmysql.org/
Perhaps it's not a "blog", but it never hurts to watch the original (c2) wiki . The link is to the quick changes screen so you can see all the recent edits. http://www.c2.com/cgi/quickChanges
If you code in Perl, following the "journals" at use.perl.org  is nice. The front page is OK, but I find it much more useful to follow the personal journal pages of the developers whose modules I use. http://use.perl.org/
Shameless plug: FettesPS  http://www.fettesps.com
If broken it is, fix it you should  - Tess Ferrandez, ASP.NET debugging, performance, etc.
Faculty of the mind  - Fredrik Kalseth, Test Driven Development, Best Practices, etc. http://blogs.msdn.com/tess/
Kent Beck's blog  (Programming guru extraordinaire - among other things, creator of Extreme Programming and Test Driven Development) http://www.threeriversinstitute.org/blog/
ASP.NET: 4GuysFromRolla . http://www.4guysfromrolla.com/
Occasionally you can find gold bits in the MSDN Blogs  http://blogs.msdn.com/
Two community news/vote sites. http://dotnetkicks.com/default.aspx
The Morning Dew  (although as I'm in the UK it tends to be the Lunchtime Dew for me!) http://www.alvinashcraft.com/
DNRTV.com ... .NET Rocks vcast