Kiss n Fly is a good time, though the bitchy gays are usually found there. Some fun and rowdy people show up around 1230.
Rain has cheaper drinks and a slightly less pretentious atmosphere.
OCH is between the two and is rowdy and a bit on the "dirty" side. It's a lot of fun once it gets hopping, and a lot of nice people go there. This usually has good conversation on the patio.
Dancing is generally best at KnF, but don't neglect Phoenix across the street, which is not gay but is quite nice. With a trip up the stair to check it out.
Enjoy your night in Austin!