I am starting work on an open source TIGER based gps navigation engine for both windows and linux, but it wont be ready for a VERY long time (probably 4 months to a year).
In the meantime, your kinda out of luck. If you want a demo of iguidance ill be happy to let you remote control my car computer over the internet one day.
Freedrive and centrafuse come with demo maps and applications for destinator.
GPSdrive is a crappy GIS program for linux, but doesn't really do the job you want.