I used this software in both Paris and Seoul lately and it was a lifesaver. The problem particularly in Seoul is that their subway system is so big and their use of English so limited that unless you speak Korean you can spend a long time looking at small maps trying to figure out how to get where you are going. Lots of features such as fastest route, # of stops, estimated trip time, return trip etc make this a fantastic program for over 250 cities. You only sync the cities you need. And the best part is it's FREE.
http://nanika.net/Metro/
