Gonna make this quick because I'm late for the airport (San Francisco, here I come!). Amazon has the refurbished TomTom One 130 GPS for $47.98 shipped.
That's after a $20 mail-in rebate, but still. The TomTom 130 has some pretty decent features for an entry-level GPS, including text-to-speech and an optional traffic receiver.
You can also have a little fun by adding celebrity voices. Remember the Homer Simpson GPS from a couple weeks ago? You can add that voice, and many others, to the 130.
Amazon doesn't list the warranty, but because this is a refurb, assume 90 days.
I know nobody likes rebates, but when you take that into account, this is the lowest price I've seen yet on any GPS. If you don't already have a nav system for your car, you'd be crazy not to hop on this deal.