I feel the same way. I have to drive about 15 minutes to have some decent riding trails. I did just purchase a new Trek 520 that I use to commute to work because I wanted a more "road" bike feel.
I am thinking of switching to my mountain bike for the commute though. I ride on a pretty rough rail trail part of the way, and lately I am missing my neglected mountian bike
I agree with most posters about needing motivation to drive...I know I always have a blast once I get there...just hate the drive.
I am thinking of planning a mountain bike oriented vacation (Moab??) as my motivation to get out there and ride