Here's a hack that allows you to sync your iPhone to multiple computers. It works with music, but I'm not sure if it does with apps:
http://www.andrewgrant.org/2008/03/30/how-to-sync-an-iphone-with-two-or-more-computers.html
http://www.andrewgrant.org/2008/03/30/how-to-sync-an-iphone-with-two-or-more-computers.html
