A couple of programs that have made my life considerably easier.

GPX2POI - Convert POI-files to GPX-files like a real GPS-junkie.
If you don't know what that means, you probably don't need it.
CPtoGPS - Wonky Toolset I made to convert a hardcopy list of scouting-style Dutch-Grid coordinates (Rijksdriehoek) to a GPX-file you can put on your GPS-device.
Created for scouting game called Hike and Seek, which starts with a short period of about an hour where you have to plot a ridiculous amount of coordinates on a map, and preferably to a GPS-device too.
(instructions are turbid and in Dutch)
Rijksdriehoek GPS (external) - Only Andriod-App I ever found that converts your phone's GPS-co÷rdinates to Dutch-Grid coordinates (Rijksdriehoek).
Edit: Yes, this is pointless app if your not on Dutch soil, thank you very much.
Muzecast (external) - Server-client system for streaming music from your Windows-PC to your Andriod-phone.
To listen to your amazing eccentric music collection on the go.