Attention Dropbox Users: If you use dropbox anywhere near as much as I do, you probably keep it almost full all the time. While you've always been able to get more free space by inviting others to join, this can be more difficult that it sounds. (I've told many people about Dropbox, but only managed to get two to sign up through an invite, netting me a measly 500 MB of space ;( ) Rather than attempt to track down non-dropboxers, you can test a new feature in some of Dropbox's beta versions that automatically uploads pictures and videos from cameras, cellphones, SD cards, and other devices. The first automatic upload will net you 500 MB in free space, and for each additional 500 MB of data you upload, you get another 500 MB, up to 5 GB. For more information, check out the following posts:
-AppleSky
EDIT: And of course, if you've never used Dropbox and want to try it, let me know and I can invite you, and we both get free space :)