are you looking for just a map? or "which train/stations should i use" functionality?
if it's just the map, find a good one and email it to your BB and store it as a pic. it's low tech, but it's effective
surf around the Metro website - I'm sure you can find something there that's useful. http://www.wmata.com/tripplanner/maps.cfm
oh - hey - that's cool - they've superimposed the lines on a google map!