I've liked Streets and Trips from Microsoft for a while now. I just got the 2005 version with the GPS receiver, and this is so cool. It retails for around $130 (US) - so maybe you can find a cheaper GPS and just pop for the base software, but the GPS is pretty reasonable all things considered. I took a cruise around town with my son navigating on my tablet and they GPS stuck on the windshield and it was pretty accurate.
I've used my older version (sans GPS) to plan a week long motorcycle trip in 2003 and the results were great: maps were accurate and directions right on, even in rural areas.
If you can find this on the cheap, it's pretty fun to use. I'm wondering what I can hack the USB GPS to do other than just using it in the application though.

• Maybe make a black-box for my car that logs the data, then uploads it into Streets and Trips for a graphical view of my voyages
• I want to hook it to my PDA (Streets and Trips comes with a Pocket PC Version too) and rig up a mode to power the PDA with 12 volts from my motorcycle, and mount the PDA to the tank or windshield (yeah, I know ... call me a wuss with a windshield) for long trips or 'getting lost' type cruising. I was thinking that a little wheel that rides along the tire should generate enough rpms to create 12V, with a little capacitance and voltage regulation ... and the PDA does have a battery to keep it going on extended stops ... Hmmm, don't those bicycle headlamps work like that? (they did when I was a kid ... but Banana Seats were cool then too) ... I'll have to try that. I'll still need a Compact Flash USB host for the PDA.