Push Notifications, Maps, Peer To Peer Connectivity and iPod access - those are the primary upgrades that came with iPhone OS 3.0 and there are a lot of apps out there using them.
Unfortunately, not many of them are great.
So we've cherry picked the best ones we've found so far and added them to our newest Applist. You can check it out here. We've got Textfree, Boxcar, TuneWiki and more, but there's still space for a few more.
I'm still waiting for Mover 2 to get approved so I can begin Peer to Peer photo, bookmark, text and contact sharing. That one is going straight to the top of the list.
Let us know if you think we should add another app onto the list.