Loc: Eastern PA, USA
As usual, there are a few ways to go.
I share .WAV files via broadband. This is the most secure, platform-independant way of sharing data. But the files are huge.
There is a compression format called .OGG. Some folks claim that they are getting good timing sync exchanging .OGG files.
The other way would be to get a program that creates/restores an image of a CD, then share that info. If you're sharing between two similar workstations, this method transfers the whole project.
You need either some web space to host files, or you can run a personal FTP server on your PC, and your friend can upload song data to you or download it from you as long as you are both on-line at the same time. I have webstorage, so I can just post tracks for pickup, and I don't have to stay on-line for the recipient to DL them.