Unfortunately while it is possible to repair if you have the skills I rarely see broken USB port N900's up for sale on eBay from people with an expired warranty.
I feel that many of the thousands who have posted here in this thread, a tiny fraction of all who have broken their N900, are just junking a phone that can be made better than factory with 45 minutes of work carefully disassembling, masking, and soldering a bridge to the trimmed RF cage on one side and some scraped bare ground plane on the other.
I have dropped my repaired/upgraded N900 about a meter onto pavement with a USB cable in and it bent the cable tip, I had to use a pliers to remove it but the port was fine.
If you break your N900 there are plenty of people who would bid at least $50, it would at least give another user a chance at a great machine.