Currently Being ModeratedDec 12, 2012 1:43 PM (in response to dubwise)
Using iCloud you can share your GarageBand projects with all Macs, that are signed into the same Apple ID account, so you can use that only to share projects between your own macs.
To share with other musicians I'd recommend Dropbox; this will let you store your project in the cloud and send links to friends, so they can access the project.
When you save your project to disk, I'd recommend to save it as an archive project. This way all your custom loops used in the project will be included, and your friends will be able to use them.