Is it possible to transfer music from your iPhone to an iTunes Library?

Basically my MacBook crashed with all my music on it and they can't replace the music. Is there any way to take the music from my iphone and transfer it to my macbook (especially since I want to download the new 2.0 update and it has to delete your music in order to update).

I tried "Check for Purchases" and it only downloaded 2 songs.

Thanks, any help would be appreciated.