nice! I'm going to have a 1 day layover there in a couple weeks.
the tourist things to do seem like taipei 101. pay the extra to walk up the 2 extra floors at the end onto the observation deck.
the national palace museum is supposed to be one of the top 3 museums of the world.
the zoo is supposed to be the largest in all of east asia.
and, you already hit the night market =).
http://en.wikipedia.org/wiki/Shilin_Night_Market is supposed to be the biggest one....