If it has to be cheap, stay away from Intel chipsets - these are expensive enough to drive mainboard cost up.
Use something made from SiS 630/730 for Celeron/Duron - these all-in-one single-chip monsters have almost everything a system needs - VGA, sound, modem riser support, LAN, and six USB ports.
Unlike the previous poster, I've had good experience with PC-Chips gear. Their M810LMR SiS 730S board sells like hotcakes, and people are generally happy with it. One word of caution, PC-Chips don't do end user business, hence no end user support beyond BIOS updates either. You got to know what you're doing to use their boards successfully.
regards, Peter