Although I'm mostly into Linux now, this instructable shows you how to generate your maps with windows tools. It's just a first shot and I wanted to keep track of what I was doing, because this stuff is really confusing, especially if you are switching from windows to Linux. The good news is, most of the used software is also available for linux, so it's just a small step.
Beside the fact that this is confusing in the first place, I'm limited by the fact that my device only accepts 2GB micro-SD cards. This is not really much if you want to have some data on your device. The bike-map for germany is 1.2GB already, if you would like to add the alps and france or spain you get a problem here. By selecting individual tiles you can reduce the size of the final map to the area you really need.
No need to buy a new device right now. In one or two years from now, Galileo the european GPS will start operation and be much better than the existing.
Step 1: Get the map data
There are many others providing the same service and similar outputs. Another famous source for maps is this website: http://wiki.openstreetmap.org/wiki/User:Computerteddy
Here you get a lot of precompiled tiles and also some final maps for upload to GPS-device.
What do we get?
When downloading a map from the first website, you get an installer for windows. But in fact it's just a self-extracting zip file and you can also open the exe with 7zip.
So unpack it into a folder of your choice.
There you have the map data!
PS: I chose the map of south africa because it is quite small and processing very fast, you can do this with any map and any tiles.