I've had an interesting idea for music collaborations. There are some online storage services emerging that essentially give you a new hard drive (e.g. I: or I drive) that is actually saved to your account on the internet.
The kicker is that some services let you have shared folders which keep in sync with multiple users. And they are often free. So in theory, you can upload a couple of audio tracks with an Audacity etc project file like "StrawberryJam01.aa" which is automatically downloaded to your collaborators hard drives. Then, if they add an audio track, modify the Audacity project file and save it as "StrawberryJam02-With Drums.aa", these files also get automatically downloaded to all collaborators. Sounds like it has potential (excuse the pun).
Examples include xdrive.com (more limited and now apparently closing down), the unofficial GDrive (turns your GMail space into a Drive http://en.wikipedia.org/wiki/GMail_Drive) and Windows Live SkyDrive (skydrive.live.com). Wikipedia has a list of File Hosting (http://en.wikipedia.org/wiki/Category:File_hosting) and Cloud Storage (http://en.wikipedia.org/wiki/Category:Cloud_storage) providers.
SkyDrive gives you 5gb for free, Windows Explorer Integration, provides RSS notifications of changes and allows files (e.g., the final version) to be made public and embedded/linked to in a website - I guess we can't hold the fact that it is a Microsoft product against it, although there appears to be some others out there.
UPDATE: I've just noticed this article about Gladinet - a free utility that can mount a variety of online storage services (Google Docs, Picasa Web Albums, Windows Live SkyDrive and Amazon S3 Storage) as a virtual drive, and share with friends. Another option to consider.
Keywords: Cloud Storage, collaboration, File Hosting, JammTools, music, music collaboration, online storage, SkyDrive