So many great ones from xkcd, but this is still my favorite:
To get it out of the way up front:
Alt text: Are you stealing those LCDs?' 'Yeah, but I'm doing it while my code compiles.'
This is my favorite. I LOL every time I see it.
Source  http://theoatmeal.com/comics/design_hell
Who says programming doesn't pay off?
I've always liked this one 
I've put this to the test on many late college nights.
While it is not specifically about programming, it is good for perspective.
I personally like this one
One of my favorites from long ago. I think I lived this at least 3 times during the late 90s before the .com implosion:
I find that I can interpret many non-programming cartoons as programming-related. Here's one from Peanuts from 1984(!).
This was exactly what was happening on a game I was working on many years ago, the schedule was tied to the date of the E3 trade show and all the tasks required to complete the project were scaled to fit.
I've had the 'scale the timelines to fit an end date' problems a few times. How I hate Microsoft Project and those meddlesome Gantt Charts.
XKCD 538  http://xkcd.com/538/
Sorry, I looked everywhere, but can't find the image. It stood on my desk at many conpanies for over a decade ....
Pointy headed boss: “You’ve been a good contract employee. We'd like to make you regular employee"
Dilbert: "You mean you want to pay me less?
Pointy headed boss: "We want you to be motivated by something other than money"
Dilbert: "Like stupidity?”
update: Thanks, here it is:
XKCD 208 . http://xkcd.com/208/
Way back in the dark ages there was a Foxtrot toon that was so exceptional that I scanned it in. Waiting for it to appear on the internet was not acceptable because it would be too easy to forget. :(
Dad: SON, ALL I WANTED WAS A CUP OF COFFEE TO START MY DAY.
Jason: THEN WHY'D YOU ASK FOR JAVA.
Reminded of this cartoon by Tuhin's answer  to the "Favorite Pr. Joke" question.
Here is Wally's take: