Hmmm.. $70 - $100.
The usual Abit's and ASUS's are over that price by a good $20, so I won't go into those..
The Epox 8RDA+ falls in that range, as does the Soltek SL-FRN2-L and SL-FRN2-RL (differnce between the two is one has SATA Raid, the other doesn't). You could also consider the MSI K7N2 Delta-L and get the new nForce2 Ultra chipset, or go a little cheaper and get the K7N2-L.
-The Epox and Soltek boards have lockable PCI/AGP, not sure about MSI though.
There are a few other brands that fall in that price range, but I wouldn't recommend those models..
I think your best bet is the 8RDA+ or either of the Soltek boards, or you can be one of the first to have the MSI with the NF2-Ultra chipset.