I'm not so sure about the AMD side (I'm more of an Intel man myself), but I know AMD has their 8000 series chipset for the Athlon 64, Via has some other chipset as well, and, as Schadenfroh mentioned, nVIDIA has their nForce3.
Over on the Intel side, Intel themselves will not be releasing a desktop chipset for a little while, I believe (well...the i865+integrated graphics...but I don't think that counts). Via is working on a dual channel DDR chipset, since they now have an Intel bus license. SiS is working on one as well, but they also have a quad channel RDRAM chipset (the R659) in development. All of these 800MHz FSB platforms should support for Prescott (probably through a BIOS update), since it's supposed to be socket 478 compatible (initially).