For AMD, there are some chipsets developed, but the most succesful (and overall most performant) ones are based on the nVidia nForce4 chipset... They come in four (five?) flavors:
nForce4-4x: The budget one, currently most used for Socket 754 motherboards... These boards generally lack features like FireWire and the nVidia Firewall, but do come with Gigabit LAN most of the time...
nForce4: The vanilla offering, there are a lot of motherboards out there with this chipset... You have some Socket 754 mobo's with it, but these are generally preserved for the Socket 939 line... The boards feature the Firewall normally, but dare to come without FireWire as well...
nForce4 Ultra: The full-fledged nForce4 variant and the most expensive one (without taking SLI) for single video card configurations... These boards have all the features you want (some have a dual Gigabit LAN integrated etc.)...
nForce4 SLI: This was nVidia's former high-end offering... It is a nForce4 Ultra (with its features as well), but only differs in its possibility to take advantage of SLI, so two video cards can be used for maximum performance... These two cards divide the PCIe 16x available, so both has the speed of 8x at its disposal... This causes no inferior prestations however, as even current high-end graphics cards don't saturate the bus...
Then you still have the nForce4 SLI 16x... While this may be considered as another flavor, it's just an evolution of the genuine SLI version... The big difference is that this one offers two lanes with PCIe 16x... These boards aren't widely available yet, and don't really offer a huge bonus over the regular ones, except for their price...
All these chipsets are orientated for use with PCI-Express graphics cards... They don't offer DDR2 compatibility however... That is preserved for Socket AM2, due to halfway '06...
EDIT: You still have offerings (other chipsets) from other manufacturers, such as ULi, Via and ATI, but the nForce4 variants are the ones used mostly...