I'm sure you can store at least 1000 waypoints but the real geocaching daddy is 'custom points of interest'. If you use GSAK (and if you don't, you should) have a look at the macro list in particular 60CSxPOI. You can store thousands of caches including brief details and clues
It must be me as i have a 2gb card in it and i am sending them over as cache's which once there is fifty save it wont do anymore. I will have a try at the other ways that some people have suggested Thanks