Geocachers use a wide variety of software in pursuing their sport. This includes programs for mapping, managing their waypoints, and other uses.
A handy program to have on a laptop, especially when doing paperless caching. You can load up all the area caches, plug in your GPSr and autoroute your way from cache to cache. The one big disadvantage is that it cannot directly import GPX or LOC files. You need to use a separate program to convert the waypoints to a CSV file. Streets and Trips also allows you to create custom icons for all your waypoints, so for example, you could load in all your caches by type and give different icons to the traditionals, multis, virtuals, etc. Streets and Trips is Windows-only, and can be found cheap at Sam's Club.
ExpertGPS is a combination waypoint manager and mapping app. It can read and write waypoints, routes, and tracks to and from your GPSr. It can also read GPX and LOC files from Geocaching.com. It's main feature is the ability to download satellite and topo maps on the fly from the internet. Unlike a mapping app like Streets and Trips, you must be connected to the internet to download maps. ExpertGPS caches the maps it downloads, so you could pre-download an area of maps before going out caching. A handy feature is the ability to bring in "scanned maps." If you were holding an event at a park which has a large number of caches, you could load up a park map from the internet of scan it in from a brochure and superimpose the locations of all the caches. ExpertGPS is Windows-only and is shareware.