Now I found a spare 2gb sd card laying around so I decided to put Debian on it. It was pretty easy but I can not boot it. I think the problem is around the kernel. It was not really clear for me how to install it so I created 2 partitions on the card. The firt is around 20-30 mb for the kernel because the U-boot will search on it and the second for the filesystem itself.

http://elektranox.org/n900/index.html

I hope somebody can help me how to make it work, and I really hope that installing and configuring it will help this thread also.