Most rpi distributions use hard float which means binaries won't run on n900. If you use an armel distribution (or use multiarch), some binaries could run, but you would probably end up with unresolved symbols / wrong glibc hell on anything more serious.

I often compile stuff on Sheevaplug running Debian and often the binaries run just fine on n900. So you can run older arm binaries on newer but not vice versa.