I recently comitted a driver I wrote for the integrated audio in the VIA
VT82C686A southbridge chip found on some motherboards. The driver is
named "auvia".

Sample dmesg information from an Asus K7M motherboard:

auvia0 at pci0 dev 4 function 5: VIA VT82C686A AC'97 Audio (rev C)
auvia0: interrupting at irq 10
auvia0: ADS64 codec; headphone, Analog Devices Phat Stereo
audio0 at auvia0: full duplex, mmap, independent

If your motherboard has this chip and uses the integrated audio (the
iOpener, for example, has the '686A but uses a Yamaha chip for audio
instead, others just don't have audio at all) please try it out and let
me know of any problems. 

Thanks to everyone who helped me with this, in particular Soren Jorvang
for getting me started and finding docs on the chip, and Charles Hannum
for debugging help.