It is great, as Lisp is very good for prototyping and solve simple problems fast with a 5 minutes snippet (e.g. calculator for statistics). Anyway, the thing more I miss to run in my N900 is the GNU C/C++ compiler (it is possible in the SDK, but because of library dependencies it is not yet possible in the actual device -someone has to do the work-). As alternative, I didn't tried yet to use the Fabrice Bellard's TCC ("Tiny C Compiler"; may be it works off-the-shelf, as it contains ARMv4 support -i.e. no Thumb2 opcodes, meaning larger binaries-, done by Daniel Glöckner), but may be I'll try it some day.
golang for maemo comes with the plan 9 c compiler. not sure whether you can use system libs with it, though.
Thank you for the advice. I tried it, but unfortunately, unless I miss something, and although 5c compiler is there and seems to work, the problem is that header files (e.g. stdio.h) are missing (the golang is installed at /opt/go, containing /opt/go/pkg/linux_arm and /opt/go/bin).