Re: Remote Backup
Do you really mean to limit them to 500MB each? If so, save yourself the effort (and cost) and use Dropbox - you get 2GB online storage which is autosynced onto as many computers as you like, with a web interface too, for free.
If you mean 500GB, then you must be very rich! A dedicated server with enough capacity for that, for you and your mates, will cost loads. In that case you can afford to buy someone's ready to rock offsite backup solution and save yourself the bother.
If you really want to have a go, I'd suggest looking at ssh and rsync for the server. There are several GUI backup apps that use these for the clients.
"Answers satisfy the mind, mysteries capture the heart." -- David Gate