Hi Maarten
I've just bought a share in a Jodel DR221 (well, it's almost a Robin!).
A very good place to start is
www.jodel.com which features stacks of history on the Jodel/Robin evolution.
Also, there's a [jodel] group on Yahoo (
http://groups.yahoo.com)
In the case of the DR221 for example, it is a good choice IMO as it has a good power/weight ratio & good lift using that wooden airframe and cranked wing. This utilised typically on smaller engines, which are more fuel efficient. They may not have the STOL performance of say a ragwing Piper, but do benefit from a higher cruise speed.
BlueRobin