Matt,

For viewing topo maps, I recommend downloading Garmin's free desktop map viewer, MapSource. MapSource and other free map-viewing applications are available here:

http://www8.garmin.com/support/mappingsw.jsp

Once you have the map viewer, you will still need to actually acquire maps to load into it. You can buy Garmin's maps, but that is an expensive way to go (100 bucks for the 1:100000 US topo). If you want free maps, I recommend Ibycus Topo USA. It is the most popular free country-scale topo, and is available for download here:

http://www.gpsfiledepot.com/maps/view/19/

The Ibycus map is definitely compatible with MapSource, although I can't vouch for its compatibility with Garmin's newer BaseCamp software. Once you've loaded the Ibycus map data into MapSource, you can either print out maps or download them onto a Garmin GPS unit.

Good luck!

Alex