Here's some rather strange news. Asrock is selling a new 790GX mATX board based on AMD's ancient Socket 939.
It packs four PC3200 DDR slots, 1 PCIe 2.0 x16 slot, as well as two PCI slots and a lone PCIe x1. There's even an eSATA port and the board features HDMI, VGA and DVI outputs, courtesy of Radeon HD 3300 graphics.
It all reminds us of AMD's golden era, the good old K8 days, but the board really isn't aimed at the nostalgic crowd. It's more of a replacement part or a convenient way to recycle ancient hardware and bring it up to spec, particularly in the video department.
At €61 it's good value, too. Bear in mind that your dusty K8 coupled with a 790GX should have no trouble wiping the floor with Atom based systems, so it's probably a better choice for HTPC rigs, despite higher power consumption.
You can get it here.