My small business just found out about DropBox. They give you a couple GB free to start, and you can upgrade to like 50GB for $99/yr. The security and ability to sync and share are really flexible and we've pretty much developed a dependency on it by now, since we have several small home office locations and need to consistently access a body of shared files.
The promotion going right now is that if you invite people who install the program, you get additional space for free. Check it out:
http://tinyurl.com/getdbox.