Now that Comic-Con is out of the way, it's time to be hosting and posting about Matt Bortolino's incredible Half-Life 2: Episode Two mod Research & Development, one of the few must-play mods to hit our desk in a while.

Research & Development takes the non-combative approach of Portal into the gritty environment of Half-Life 2, and does so with a refreshing amount of original mechanics and crafted special effects. Here's a mod that not only delivers a unique, gun-free experience, but one that effortlessly introduces fresh Source engine effects at surprising regularity.

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The mod begins with little pomp, the player awakening in a detailed but generic location. A sign on the wall announces that this is a "weapons free zone," while... Read more

Update: The mods are now available for download and can be found under the "Not Installed" portion of Steam's "My Games" section. In addition, Valve has put Half-Life 2: Episode One on sale for $4.99, offering cheaper access to the Source Engine.

The mods, playable for anyone with a Source Engine-powered game like Counter-Strike: Source, Half-Life 2 or The Orange Box, are:

• Age of Chivalry
• D.I.P.R.I.P.
• Insurgency
• Synergy
• Zombie Panic: Source

Original Story (10/2/08): As promised earlier this week, Valve is scheduled to make five user-created mods available on its Steam digital distribution service later today.

Additionally, the mods tie in to the Steamworks toolset, providing community services and automatic updates like full retail games.

Expanding the breadth of its online PC digital distribution platform Steam, creator Valve has announced that it will begin offering free downloads of user-created mods.

Playable so long as a user has a Source-powered game installed--such as Counter-Strike: Source, Half-Life 2 or The Orange Box--the mods will appear under the My Games listing, and will receive automatic updates like any other Steam release.

The initial batch of mods slated to arrive this week are:

• Age of Chivalry
• D.I.P.R.I.P.
• Insurgency
• Synergy
• Zombie Panic

In addition to automatic updates, the mods will incorporate other aspects of Valve's Steamworks toolset, with the company promising that this will result in "stat tracking and tighter integration with the Steam community."