If you have Windows, there are a number of offerings, some of which come with the purchase of a GPS and then there's National Geographic...

If you have a Mac, there's Mac GPS Pro, which I am now using. I got all the USGS and Forest Service topos for my state as well. It takes getting used to as it's not so point and click as others but it's pretty snazzy and quite powerful. And of course, since you can also run Windows on a Mac, you can also get any of the Windows packages and run them that way.
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