Considering the thread's title references geocaching ...

Geocaching.com uses lat/long of the form DDD MM.MMM , so for geocaching I'll usually go long with them. I've tried to standardize my lat/long work to that format.

When working with coordinates in the field - with USGS 7.5 minutes topo maps I much prefer to use UTM coordinates.

The grids and info at http://www.maptools.com are GREAT!!

For the last few years I've purchased topo maps from http://www.MyTopo.com because (1) they come pre-printed with UTM coordinate grids, (2) I can specify custom maps that likely span multiple 7.5 minute areas, (3) I can get them printed on waterproof 'paper', and (4) their web site is easy enough to use that even I can use it with great success.