Asus has released an official listing of the AM2 boards that support AM2+ CPUs, in a total of thirteen HT1.0 boards. The other two are HT3.0 which, obviously, had to support AM2+ CPUs.
Among the HT1.0, AM2 boards are some like the M2N-E, M2N-SLI, M2A-VM and M2N32-SLI.
Albeit the added support in these older models, there are many AM2 motherboards that still don't have a new BIOS that allows for the new AM2+ processors to work in them. It's something unfortunate since all AM2 motherboards are supposed to be physically compatible with them.
Among the companies that have released new BIOSes to support Phenom are Gigabyte and MSI, in a lesser number of boards, while most companies have not yet taken action and limit themselves to support in new HT3.0 boards.
Keywords: M2N32-SLI M2N-E M2N-SLI Phenom AM2+