Haven’t had a chance to try it yet, but RoadNav is an open source GPS Road Navigation program that uses TIGER data to generate street maps and turn-by-turn directions, gives verbal commands, and doesn’t require an Internet connection. Also runs on Linux and Mac OS X, in addition to Windows. I usually drive alone, and it’s a *really* bad idea to use a PC-based road navigation program as the driver, so I don’t know when I’ll get around to it. If anyone tries it out, please let me know how it works for you.
Addendum from the comments: Check out this SlashGEO posting for links to other freeware road navigation solutions.