there's some chinese GPS in ebay that have or can be upgraded to VERY good software like Igo8...
I use it for when I don't know where I'm going aside form that, GPS can't calculate traffic jams (unless you get the traffic thingy accesory for extra) mpg for elevation differences or BEST mpg route (like the partner piwolaw mentioned with ecoroute)
edit:
http://cgi.ebay.com/2GB-5-0-A5-Thin-...item3f0225b4b9
igo8, 5 inches, 4gb inside 79$ shipped
that's a great deal even if you buy 2010 maps afterwards from a webpage for an igo device