Back on November 3, 2005, Microsoft acquired a file sharing service called FolderShare. I have been using this for quite some time and it is definitely a great solution for sharing and distributing files securely amongst your friends.
The concept is simple, you designate a folder on your computer to share with your friends. Next, drop files in it and an exact copy of that folder is created on every computer that is in the pre-designated group. The syncing works every way for every person, so the folder on everyone's computer is always up to date.
Today, Microsoft quietly changed the branding on the FolderShare site to reflect its involvement in Windows Live. Although it's not "Windows Live FolderShare" quite yet, it has been changed to "FolderShare Beta: a Windows Live Service." That's all for now, but I reccomend that everyone gives this program a try since it proves to be extremely useful.
(Thanks to ActiveWin for the heads up)