JC Baillie has hinted me to URBI, a programming environment that supports also the NXT now. Let me cite JC: URBI is
Thanks JC,
Matthias
"an easy to use programming interface forCheck it out and comment your experiences here!
robotics, which has been used so far on the Aibo. I thought you might be
interested to know that we have released a version of URBI for Lego
Mindstorms NXT.
[...]
URBI is free, with open source interfaces, and you don't have to change
the original firmware to use it. We have a forum also to discuss
technical matters here:
http://forum.gostai.com/viewforum.php?f=16 "
Thanks JC,
Matthias