Mangoes

The nightlife in Kitzbuhel is ace! Mainly because noone does apres quite like the Austrians, but the combination of party-hard season workers and some great bars really make this resort what it is.
Kitzbuhel is generally quite expensive, but befriend locals and they'll show you the cheaper spots.
Grieserls bar does great chicken wings and ribs to pick at in the evening, in a very casual and welcoming atmosphere. Then there's the Londoner in the centre of town where seasonnaires tend to gather. Highways is a bar/club with a retro american look, and a table in a car. They have hot bar staff there too, though the place gets very very crowded.
The best bar in town has to be Mangoes. Its less obvious so not as packed at Highways, though it fills to capacity quite easily. The place is run by Sugar, and awesome guy who runs themed nights regularly, offering free shots and drinks to those who turn up in costume. Its also open until about 8am, and trust me its easy to stay until closing without realising.
You won't be bored in a place like Kitzbuhel....