It's been ten years since Half-Life 1 was released, but that doesn't mean the modding scene has died down any.  In fact, one of the best mods for the game has always been the Sven Co-Op Mod.  Last week the team finally release the first beta of Version 4.0 of the mod.  Along with the ability to play through the entire Half-Life storyline in co-op, players can now play through the Opposing Force add on as well as tons of custom maps.