great popular, simple units... like the Canon digital Elph of the GPS world: Garmin Nuvi 350/360/660 and Tom Tom One
350 is old line; 360 is popular new line; 660 is more expensive new line
Tom Tom has great interface and easy to use, but doesnt pronounce street names like Nuvi (ie turn right in 300 meters instead of turn right at mccoy rd)
other good ones are Garmin 2xxx series, Lowrance i500... these are good, and may have more features, but the previous have the superior form factor and out-of-the-box use.
if you have a PDA you can also get TomTom software and use it on there with a GPS receiver. thats my current set-up and works GREAT. i also have a Nuvi 360 on order but its awaiting shipment.