(CORRECTION) iDisk works across all platforms. simple webserver name and password gets you connected:

http://idisk.mac.com/%5Bmembername%5D

then type in your user name and password and you are set. It mounts like a local storage in mac and in windows (assume you can do the same in linux).

http://islandinthenet.com////2008/08/06/mounting-mob...

MobileMe also does the email link sharing with and without password (e.g., you send a link to a file instead of attaching it so you dont blow the mailbox limit). It does, however, not have file history but i think the ability to use it as a quasi local storage drive makes up for it with much easier file management.