Hi,
I only know some places in Taipei. If you like to try the local
Taiwanese snacks, you can go to Shi Lin Ye Shi (Shi Lin Night
Market), there are lots of food stall there and a gigantic pasar
malam place with many wares and cheap bargins. For somewhere
scenic, maybe you can try Yang Ming Shan, though I have not been up
there before as I was ill on the day we scheduled to go up. As for
nightlife, I am not sure what you are refering to so I can't help,
sorry.
Ok, these are some of my suggestions, hope you have a fun time on
your Taiwan holiday. 