If the goal is direct file sharing then a couple of ideas could be:
1. Set up a local webserver, and create links to the local file in an html page.
Pros: pretty easy to do (I think); familar download interface
Cons: not exactly secure (especially for sensitive files); doesn't automatically update with new files (without some clever scripting)
2. Set up a bittorrent tracker (Azureus makes this easy) and share the files using Bittorrent
Pros: fast; good for secure/direct transfer and sharing of files
Cons: takes a little time to set up; not really a viable solution if you are constantly updating the contents of the shared folder
3. Use an online file sharing service (there are loads to choose from) e.g.
http://www.allpeers.com/
Pros: easy, non-OS specific
Cons: may not be as quick or direct as either of the two solutions
4. VPN connection e.g.
Hamachi
Pros: Hamachi rocks for creating a LAN over the 'net; computers show up as members of the local network
Cons: not particularly straightforward to setup; not sure how Samba (windows filesharing on Mac) will work on it.
Anyhoo, have a go!
Good luck,
Steven