Getting a Mac to work with a Garmin GPS is a lot easier these days than when I first started geocaching. If you want to load maps you will still need either a PC or run Windows on your Mac (it makes me feel dirty every time I do it!). Garmin has been promising a Mac version of Mapsource for over a year now, but it has yet to be delivered.
I have hope though since they seem to be starting to roll out some Mac stuff. You can now get Mac versions of the POI Loader and WebUpdater.
The tool I like best to load my Pocket Queries on to my Garmin is a simple little app called LoadMyTracks. It won't manage your waypoints, but it the best tool I've found for loading information on to the GPS and is also useful for pulling off waypoints and track info.
If you want a more full-featured waypoint manager, check out MacCaching — I don't use it myself, but it might be just what you are looking for.
As far as paperless caching, I can't recommend CacheMate enough. It does exactly what you would hope, and comes in Palm or Pocket PC flavours.
Hope that helps!