Almost any handheld mapping GPS from Garmin will do what you're asking. With more money you get additional features - the least expensive units don't have the ability to display a topographic map, the most expensive will show your position on a topo map, and much more. All of them will download waypoints or tracks to a computer, where you can then manipulate the data and plot it on Google Earth or other mapping software.
Once you get handy with the GPS unit itself and some accessory software, you can download free topo maps off the internet (Forest Service, GISMapdepot, etc.) and upload them to the GPS for field use.
All of the handheld Garmin (and Magellan, the other major brand) are plenty rugged enough for field use, unless you plan on using it for a hammer.
For a basic unit with the ability to display topo maps, take a look at the Garmin ETrex 20 - often found on sale at Cabela's or other places. I like GPSCity.com for excellent selection and service, as well as great videos and advice on choosing a unit.
I also have a Garmin Montana, which not only is a great and capable handheld, but works as a great automotive GPS, and I also have a rugged mount for it to run it on my off-road dirt bikes. It's more up at the high end of the scale in price.
Also - you can find some great deals on refurbished GPS units from places like GPS City.
