I haven't seen anyone mention this yet. Not sure if it is usable but it looks like map data is available from TIGER.

I also have Precision Mapping Streets 3.0 and DeLorme Street Atlas USA cd's if you are interested in taking a look.

A quick search on google and I found some relevant links.
http://www.frontiernet.net/~werner/gps/
http://vancouver-webpages.com/peter/

Tom