The Left 4 Dead authoring tools have been in beta for a few weeks and Valve has decided they're ready for public consumption. A patch for the PC version coming this week will allow any old Bill, Louis, Zoey, or Francis to create and share their own campaigns.

The official Left 4 Dead blog gave a run-down of how user-made content will be accessed. The author of a campaign can pack up all of his new maps, models, textures, and so on into a single .VPK file. Players must simply download this file and move it into a new "Addons" folder in order to play it. You'll be able to create and join lobbies using these custom campaigns as well. If you invite friends to join a lobby for a campaign they don't possess, they'll be given the opportunity to download it.

The chief complaint about Left 4 Dead has been that there's not enough content so user-generated campaigns should go a long way toward addressing that (for the PC version, anyway). Modding tools were, after all, the reason players kept playing Half-Life and Half-Life 2 years after their release. Custom campaigns created for Left 4 Dead will be compatible with the upcoming Left 4 Dead 2 as well.