Garmin StreetPilot III GPS
Color screen with voice prompting.
This pic shows the unit mounted in the included base mount using self-adhesive (sticky tape). They also offer a "bean bag" mount to allow use in another vehicle. The bean bag is very stable.
I think both Wal Mart and Circuit City carry this model. It retails around the $1K mark, but I have seen them discounted as low as $750.00.
If you are considering the discounted route, make sure the unit you are looking at has the 128 meg memory stick (rather than the older 32 meg one) and the fully unlocked map CD.
Older units that have been discounted before contained the smaller capacity memory stick and the older map disk. Also, older units required you to pay to unlock the Map Disc. It came with a coupon to unlock one region (out of 10) in the US, and additional regional unlocks were $79.00 each. The entire disc could be unlocked for $225.00.
The curent model (deluxe kit) includes the 128meg memory stick and a fully unlocked MapSource map CD. The newer Map CD (ver 4.01) has so much additional detail over the previous ones that the 128 meg stick is almost a necessity.
Using an aftermarket GPS allows you full use of the radio system at the same time, rather than having to use the in dash setup for both entertainment and navigation.
When considering navigation gear, keep in mind that a GPS is always available without subscription. The NavStar type setups use 2way communications to keep track of your car (and you) for their services, as well as for the navigation features. With them, if you don't pay for their service, the navigation part is useless.