Still the good old V5 5500, unless ATi/nVidia suddenly decides to start producing GPU's that don't rely so heavily upon AGP's advanced feature set I wouldnt expect that to change anytime remotely soon.
Best from ATi would probably be the PCI Radeon7500LE
Best from nVidia.... I'm reasonably sure they don't have anything beyind a PCI GF4 MX420.