I'd recommend #iphonedev on Freenode for anything iOS.
I haven't had great experiences there personally. The conversations aren't the most enlightening and there's a lot of ripping on new developers asking obvious questions. I'm a decent developer at this point, but early on, asking questions in there wasn't pleasant. I'm a big proponent of encouraging new developers of asking lots of questions and those that discourage it are really not helping the community.
That said, it's not all bad. I still hop in every now and then.