ASRock has successfully improved the already excellent 939Dual-SATA2 and delivered what looks like a killer budget motherboard to me.
On the feature side SLI support has been added (a patch to enable SLI is included on the driver CD). Another nice addition is support for Gigabit Ethernet and eSATA.
While overclocking was possible on the 939Dual-SATA2 it was a bit limited, this limit is now gone too. Actually I must say this was one of the easiest motherboards to overclock, the excellent POST fault-detection mechanism added to the experience. The number of overclocking options in the BIOS has been increased, but unfortunately CPU voltage is still limited. But an easy to do voltmod can solve this problem.
The best is the amazing price of the ASRock 939SLI32-eSATA2. You can find it online for around 80 USD, I would expect the price to drop even more in the near future.
Oh wait, I forgot another cool feature. With an additional CPU riser card you will be able to use this motherboard with AMD's upcoming socket AM2 which is scheduled for release later this year. However, given the first slot card pictures it seems that you will be rather limited in cooler choice and overclocking. Still, a nice upgrade path.