I can't find one. Which sucks because I had figured there was no point me writing one because someone else was going to. I figured someone would hack http://code.google.com/p/mobileterminal/ and make it an AppStore application.
I would expect that they're under pressure to avoid offering apps that might cut into AT&T's business, such as Skype or an IRC client. An ssh client would be about as good as an IRC client.
Would be excellent for a spot of emergency server admin when away from the desk :)