If you don't have any software on it, its much, much harder. I would suggest calling local pawnshops.
If you know your IP address you can try contacting your ISP as if they went onto the same service provider they could potentially track it.
You can also check for chat clients such as yahoo, msn pidgin etc as many of those will automatically sign in. If so, you could contact the appropriate provider with a copy of your police report to get the IP address and then maybe track it.
However, without any real tracing or tracking software the odds aren't in your favor. If you havent already contact the police right away though. Alot of times if its a computer they will just pawn it. Cragislist is another good source. Look for postings with similar computers to yours.