In their most recent weekly news update, Valve announced that starting next week, Steam will begin hosting certain user-created mods of Source engine titles such as Half-Life 2 and Team Fortress 2. Owners of any Source title will be able to download these mods for free -- what's more, Valve has promised automatic updates and stat tracking for the mods they add to the download service.
The first five mods to be highlighted by Steam are Age of Chivalry, a medieval HL2 mod (pictured above); Synergy, another mod for HL2 which adds a co-op mode to the campaign; D.I.P.R.I.P., a multiplayer vehicular combat game; Zombie Panic, a spiritual precursor to Left 4 Dead; and Insurgency, a "total conversion" mod that takes players out of City 17, and places them on a modern battlefield. Sadly, our Source-based Burgertime mod didn't make the cut. Hopefully Valve will get wise and pick it up with the next batch.