Dropbox ^[1]

• Storage limit: 2 GB ^[2] (up to 8 GB by inviting friends ^[3])
• File size limit: No ^[4]
• Limit on number of files: No ^[5]
• Bandwidth limit: Yes ^[6], but they don't specify what it is exactly.
• Can link directly to files: Yes ^[7] (files must be in the public folder)
• Versioning of files: 30 days ^[8]
• Clients: Web interface, Mac, Windows, Linux (Requires Gnome/Nautilus), iPhone ^[9], iPad ^[10], Android ^[11].

Dropbox Pro ^[12]

• Storage limit: 50 GB - 100 GB ^[13]
• Pricing: 50GB for $9.99 / month or 100 GB for $19.99 / month
• Versioning of files: 30 days ^[14], or unlimited if the Pack Rat ^[15] feature is added.

Other features ^[16]:

• Computers on the LAN will be synced much more efficiently, using LAN sync ^[17].
• All files stored on Dropbox servers are encrypted (AES-256) and are inaccessible without the account password ^[18].
• It stores my files on Amazon S3 ^[19].

SkyDrive ^[1]

• Storage limit: 25 GB
• File size limit: 50 MB
• Limit on number of files: ?
• Bandwidth limit: ?
• Can link directly to files: Yes (permissions-based)
• Versioning of files: ?
• Clients: Web browser.
• Pricing: Free

SkyDrive works well for me. The file size limit is perfect for documents and photos. Plus, using 7-Zip ^[2] I can compress my backups, and split the archive into 50 MB increments. Perfect.

As per comments below, I use Gladinet ^[3] to access my SkyDrive via drag-and-drop.

I have some friends who use Amazon S3 ^[1] and speak very highly of it

Google Drive ^[1]

• Storage limit: 10 GB (up to 1TB upgrade available ^[2])
• File size limit: 10 GB ^[3]
• Limit on number of files: ?
• Bandwidth limit: Yes ^[4], but unspecified what it is exactly.
• Can link directly to files: Yes (if made public, anyone with link can download)
• Versioning of files: Yes, for Docs
• Clients: Web browser, Windows (XP+), Mac (Snow Leopard+), Android (2.1+), iOS (5.0+) details ^[5]

Backblaze ^[1] keeps an always up-to-date copy of your data in their cloud. Once you get through the initial backup (can take a week), your data is always backed up with negligible network and CPU usage for only $5 per machine per month. It's also excellent software that feels like a first-class citizen on the Mac (not sure about PC).

So, if you lose your house in a fire (blaze!), for $99, Backblaze will overnight a DVD with your data. Since that's not large enough (usually), for $189, they'll overnight an external hard drive with your data. Pricey, but it's also a worst case scenario, in which case ... an absolute bargain.

Syncplicity ^[1]

• Storage limit: 2 GB (50 GB upgrade available ^[2])
• File size limit: ?
• Limit on number of files: ?
• Bandwidth limit: ?
• Can link directly to files: ?
• Versioning of files: ?
• Clients: Web browser and desktop.

Microsoft Live Mesh ^[1]

• Storage limit: 5 GB
• File size limit: None
• Limit on number of files: No
• Bandwidth limit: No
• Can link directly to files: No
• Versioning of files: No
• Clients: PC, Mac, and web browser.

Other Features:

• Allows you to sync to a folder on your desktop (similar to Dropbox)
• Individual sharing options for each folder
• News feed that shows you when a file was modified

Note: Live Mesh is going to be replaced ^[2] by Windows Live Sync ^[3] soon.

I use the combination of Amazon S3 ^[1] and Brackup ^[2]. It can also target CloudFiles, FTP/SFTP or a local file system (across a network share for instance).

Brackup:

• Pros:
  • Free
  • Incremental backups
  • Encryption
  • Roll back to any previous backup log
  • Very configurable
• Cons:
  • Command line (may not be what most people want)
  • Written in Perl, so you need to mess around with installing that, then getting all the necessary libraries installed using CPAN - it's a bit of a pain.

Amazon:

• Pros:
  • Unlimited storage
  • Unlimited bandwidth
  • Very cheap storage ^[3] - $0.15 per GB/month (Dropbox works out at $0.20)
  • Free transfers in until November
  • Only pay for what you use
• Cons:
  • A bit trickier to set up than a dedicated backup service

I think the last pro-point is the most important. With other services you usually pay up-front for 'up to 50 GB' or something, even if you're only using 3 GB. I currently pay about $3/month for my backup storage (~20 GB I guess), which is less than pretty much any other online backup provider I've found.

For the truly paranoid (who isn't?) there is Tarsnap ^[1]. From the website:

Tarsnap is a secure online backup service for BSD, Linux, OS X, Solaris, Cygwin, and can probably be compiled on many other UNIX-like operating systems. The Tarsnap client code provides a flexible and powerful command-line interface which can be used directly or via shell scripts.

It doesn't yet support Windows (except for Cygwin ^[2]), but the truly paranoid wouldn't use Windows anyway, right? It is Amazon-S3 backed and really well priced (that is, affordable).

It doesn't come with a GUI, but since it is command-line based, you can easily script it (nightly backups, keeping n previous backups). If you manage your key wisely, you'd also be able to synchronise files across computers, since the archives behave like 'tar'-archives.

I've used Dropbox, Live mesh, Syncplicity and a lot of the other services. I had a very specific need, which was basically a shared network drive hosted online instead of on the local network. For this, none of the above really shines. It's a while ago I've tried them though, so things might have changed.

In any case, I use http://www.novadrive.net/ which creates a new drive letter on your PC, where everything you store is stored both locally and online. You can invite colleagues etc, so they can access the "network drive" as well.

It works on both PC and Mac.

My 3-person web shop has recently started using LiveDrive ^[1] as an alternative to an office server. It syncs a "LiveDrive Briefcase" (mapped to a drive letter, e.g. L:) on your computer with the online storage; you have fine-grained control (at the folder or file level) over what gets stored locally on your drive. Files that you choose not to store locally are downloaded when you need them. It's all seamlessly integrated with Windows.

There's also a backup feature; right-click on any folder to silently back it up online.

Around $17/month or $150/year gets you unlimited storage.

Wuala ^[1]

• Storage Limit:

  • 2 GB+ Free. There are a few coupon codes which can easily get you ~10 GB or more:

    CONNECT-WITH-SUPPORT (1 GB, valid one year)
    2012                 (4 GB, valid two years)  
    I-KNOW-DOMINIK       (1 GB, valid 3 months)
    I-KNOW-CAROLA        (1 GB, valid 3 months)
    I-KNOW-FABIUS        (1 GB, valid 3 months)
    I-KNOW-LUZIUS        (1 GB, valid 3 months) 
    I-KNOW-MARCEL        (1 GB, valid 3 months)
    I-KNOW-MARIUS        (1 GB, valid 3 months)
    I-KNOW-DARIO         (1 GB, valid 3 months)
    I-KNOW-MARKUS        (1 GB, valid 3 months)
    SKYFISH-IS-COOL      (1 GB, valid 3 months)
    I-LIKE-POLAND        (1 GB, valid 3 months)  
    

  • you can earn up to 3 GB trough invites (250 MB per invite)
  • you can buy space ^[2]: 10 GB cost 19€ - 1 TB cost 649€ (per year)

• File size limit: 14 GB

• Bandwidth limit: I don't know (Don't think it has one)

• Versioning: Yes

• Clients: Windows, Mac, Linux and Mobile

• Can link directly to files: Yes, if they are set to be publicly visible

• Other notes:

  • it appears to be the most secure ^[3]:

    When you store a file in Wuala, the file and its metadata (e.g. name, description, tags, etc.) gets encrypted before it leaves your computer. Every file is encrypted with a different key. The list of these keys is encrypted with your password and stored on our server. Your own password is very important here: it never leaves your computer, so we do not know it. Hence, not even we can access your data.

  • you get a nice virtual drive from where you can sync your files

  • you can trade your free space for more Wuala space (or buy space) (removed from latest versions)

  • you can stream videos, music etc.

MediaFire ^[1]

The maximum file size is 200 MB for free accounts.

Windows Live Sync ^[1]

• Storage limit: 2 GB
• File size limit: ?
• Limit on number of files: ?
• Bandwidth limit: ?
• Can link directly to files: ?
• Versioning of files: ?
• Clients: PC and web browser.

SugarSync ^[1]

It comes with a 5GB free plan. But its hard to find the link on the site, since its cleverly hidden.

Here is the link ^[2].

Amazon Cloud Drive ^[1]

• Storage limit: 5 GB ^[2] (paid storage plans with up to 1000 GB of space). Buy an MP3 album and get 20 GB of storage free ^[3] for a year. Any Amazon MP3 purchases that you elect to store on your Cloud Drive at the time of purchase do not count against your storage quota.
• File size limit: 2 GB (100 MB for .mp3 and .m3a)
• Limit on number of files: No
• Bandwidth limit: ?
• Can link directly to files: No
• Versioning of files: No
• Clients: Web interface, plus Mac and PC for the Amazon MP3 Uploader ^[4]

Other features:

• Play your music in Cloud Player for Web
• Enjoy your music on the go with Cloud Player for Android (only available in the US)