only if you have already taken the steps in this thread to install tracking software

however, and this requires cooperation from the police, ISPs and mobile operators (who may or may not understand or care)...

if you know the IMEI of the device then report it to the various mobile/cellphone operators and they will be able to bar it; also report it to the police and they may subpoena the mobile operators to see if the n900 has been used as they will be able to track it down to a vague location which might identify a known criminal

if your n900 is set up to login to various IM and mail services then those providers might be able to give you IP addresses and times of access which could allow it to be tracked to a specific location