I got the Shuttle MN31N for my mom's new system. I threw in a leftover 1GHz Duron and a couple of Crucial PC2100 modules for now, and it runs Half-Life Platinum Edition great. The MN31N's BIOS is more tweakable than the Asus micros, if that matters at all.
If you don't even need USB 2.0 or 333MHz FSB support, you can't go wrong with the Asus A7N266-VM/AA. Passively-cooled northbridge, takes all 266MHz-bus AthlonXPs, stable as heck, under $60, 3-year warranty, and has the MCP-D southbridge with two flavors of S/PDIF-out (laser & coax) in case you ever want to hitch it up to a home theater system. The onboard video is certainly a step down from nF2 IGP but still, I've played UT2003 Demo on one... and you can ask Engineer whether it constituted a handicap to me or not, LOL... :evil: You can also get a plug-in accessory card from Newegg for about $25 that gives the onboard GF2MX a DVI-out, which I think makes it dual-head.
We now have 36 A7N266-VM/AA's at work and they are great. I didn't pick it for Mom because I did want USB 2.0, Firewire and the better IGP of nF2.