I've had a Garmin eTrex Vista for over six years, and it is great. Very durable and reliable, easy to use, but with a lot of advanced features. I don't make a road trip without it.
The newer models have USB ports, removable memory cards, and color screens, all of which mine lacks.

ayuh, it all depends on the $ you want to spend, I have a very basic etrex, and the newer model that drifter mentions. Garmen is decent. I think either of the two major brands would do you well (Magellen I THINK is the other brand)

I like my Garmin 60Cx, bought it last fall. Has a big color screen and expandable memory for street maps (purchased separately). I think it was $250 on amazon.com

My $.02 on a minimum requirements for geocaching gps:
You're going to want to get a portable/waterproof model (not one mainly used for driving).
Make sure it can upload map data and store many waypoints (min 50).
Routes and backtracking abilities are nice extras.
Needs to receive at least 12 satellites/channels.
Color is more expensive, but it's going to be a lot nicer to look at (esp if you also use it for driving).
AA batteries are easy to replace on the fly, vs rechargable battery systems.
Personally, I'd rather get a gps from the biggies (garmin, magellan) rather than some tiny company I've never heard of.
More here (though I'm sure you've already seen it): http://www.geocaching.com/about/buying.aspx

Best piece of advice: put that baby on a lanyard when geocaching! :D

I've got an old Magellan and a Garmin Rino. Both are excellent and I Geocache with them all the time. It's fun to have a second unit when seeking co-operatively (or as a backup if one goes down).

For basic geocaching, you don't need anything spendy or fancy, but stay away from Cobra's line. They're small and cheap, but when you get within 100 feet of your waypoint, they stop navigating. Useless for geocaching.

My dad just bought the Lowrance H2O color and it is awesome. Cant wait until I can afford one.

Any one of the eTrex series by Garmin will work awesome for what you want to do, and they are cheap (comparitively).

Many thanks to you all for shareing your knowledge.While I had done quite a bit of research on-line,feed back from locals helps tremendously