I wore jeans, a belt, black button up shirt (yes, tucked in =P ) birks and socks. The lunch interview was with the three co-founders of the company, one programmer and two designers, and an additional programmer. All four of them were uniformly wearing t-shirts (not tucked in,) shorts, and sneakers :)
We went to lunch at some nearby pizza place, and they asked me about the two previous companies i'd worked at, what i liked about and didn't like about those companies (always a hard question) and about what i really wanted to do (an even harder question.) They asked me a few generic programming questions, which i was able to answer pretty well from the couple hours of reading the MUD Programming Book and the article on Quake's engine. They said they wanted someone who was able to handle networking stuff and do other tasks as well, so that may fit me or may not. I have no idea what they thought of me personally.
Things ended pretty abruptly afterwards, we got back to the office, got out of the car, and suddenly started shaking my hand and saying it was nice to have talked with me, etc, and both groups, well, one group, one individual, went their seperate ways.
SInce i was in the area and overdue for an oil change i decided to call up AutoCare Express and see if they could fit me in, which they said they could, so i headed over there and waited a half hour while they changed the oil, then headed home. Got stuck in traffic for awhile, now i just sit and worry about how the interview went and wait for a response while trying to figure out what to say in the thank you email (something i always suck at)