Unlocking the iphone aside, the third party apps that are coming out now are very interesting. I think the holy grail hack for this device is a SIP client. If you are anywhere within wifi you will be able to use your iphone to make sip calls through your asterisk server or some other voip provider. My bets are on gizmo being the first to roll this out.
So far there have been two GUI iPhone Apps:
Tetris & Tic Tac Toe
And Lots of command line based programs and hacks:
SSH on the iphone
Wifi adhoc tethering
And so it begins… As if it didn’t already have enough, this device is going to be able to do some amazing things soon thanks to clever hacks and software put out by the iphone development community.