A compatible mobo would be hard to find, as the 939 socket has been phased out for a few years now, but you might be able to find one used on ebay. What exactly is wrong with your current one that makes you want to upgrade?
Nothing. I am building another computer for myself and giving the one I currently have to my father. There is nothing wrong with the one I have. Instead of buying a dual core used on ebay for my AMD 939 socket I just decided to buy another board. I just want to know which board right now is the best bang for my buck. I am leaning toward something that supports the AM3 triple core CPU.
Depending on if you will upgrade in the future or not, you may want to go with DDR3 ram over DDR2 ram; right now, the price lies in favor of DDR2, and the performance increase is negligible. If you decide to upgrade to next gen AM3 cpus, however, they may only have a DDR3 controller (right now they have both), which would mean you would have to get a new mobo. The choice is ultimately yours, so I present you with two mobos; one DDR2, one DDR3, otherwise they are pretty much the same (one has onboard gpu, but you can disable it).