Cloud Storage

Dropbox

• 2 GB Free.
• Windows, Mac, Linux, iPad, iPhone, Android, Blackberry.
• Uses bit differential file syncing to minimize bandwidth usage and increase speed of transfer.
• Keeps a one month history of file changes.
• Has robust sharing functionality.
• Pricing starts at $10/mo. for 50 GB.
• Offers a business / teams service starting at $795 for 5 users.

Box

• 5 GB Free.
• Has robust sharing functionality.
• Version control is only available in paid subscriptions.
• Syncing to the desktop is only available in paid subscriptions.
• Pricing starts at $10/mo. for 25 GB.
• Offers a business / teams service starting at $15/user/mo.

SugarSync

• 5 GB Free.
• Windows, Mac, iPhone, iPad, iTouch, Android, Blackberry, Windows Mobile, Symbian.
• Keeps the previous file versions of each file, without time limits.
• Has robust sharing functionality.
• Pricing starts at $5/mo. for 30 GB.
• Offers a business / teams service starting at $30/mo. for 3 users.

iDrive

• 5 GB  Free.
• Windows, Mac, iPhone, iPad, Android.
• Keeps 30 days of versioning.
• Performs incremental and compressed backups.
• Performs open / locked file backups.
• Robust sharing functionality.
• Pricing begins at $5/mo. for 150 GB.

SkyDrive (Microsoft)

• 25 GB Free.
• Windows, Windows Phone, iPhone.

MediaFire

• Unlimited Free Storage.
• Maximum file size is limited to 200 MB on free, 4 GB on Pro, 10 GB on Business.
• Storage is of limited duration on free.
• Pro is $10/mo.
• Mainly web-based interface.

Other Options:

• Syncplicity – 2 GB Free.
• ZumoDrive – 1 GB Free.
• SpiderOak – 2 GB Free.
• OpenDrive – 5 GB Free.
• JungleDisk – No Free Plan, uses Amazon AWS.