Here's an inexpensive way to get to Ximending from Taiwan Airport:
1. As soon as you get to the main hall of the airport, head to the left side where bus ticket counters are.
2. Look for bus ticket counter 6 which is Kuo Kuang's.
3. Inform the staff that you want to buy ticket/s to Taipei Main Station. (Ticket price as of February 2011: NT$125).
4. It takes almost an hour to get to Taipei Main Station. Inside, look for the MRT area and get on the platform of Bannan Line (Blue Line) going to Yongning.
5. A station after Taipei Main Station will be your stop: Ximen.