Valve recently announced on the Team Fortress 2 blog that they are releasing the source files to 10 of the game's maps, making it much easier for fans to customize them. They also said they'd be releasing more source files for maps and models in the future. "Here's the list of maps that are included in the update: Lumberyard, Ravine, Badlands, Dustbowl, Granary, Gravelpit, 2Fort, Badwater, Goldrush, and Hydro. For the beginner map makers out there, we hope this gives you an easier entry point by allowing you to alter or edit an existing map, as opposed to being forced to start from scratch.... We also hope that it'll reduce the amount of confusion around the game logic and entity setup required for the various TF game modes."
An update to the Source SDK that includes the .vmf source files for many of the official TF2 maps. This is something we've wanted to do for a while, especially as we've been growing the range of game modes in TF. Here's the list of maps that are included in the update: Lumberyard, Ravine, Badlands, Dustbowl, Granary, Gravelpit, 2Fort, Badwater, Goldrush, and Hydro.
For the beginner map makers out there, we hope this gives you an easier entry point by allowing you to alter or edit an existing map, as opposed to being forced to start from scratch. For example, you could start by fine-tuning cover in Goldrush, alter the layout of Granary, or tweak the amount of health and ammo in Gravelpit. Or maybe you just have a ton of ideas on how you think you could improve Hydro or 2Fort. We'd love to see what you come up with.
For the experienced map makers, we hope this gives you a variety of examples of how we design and construct levels, the tools we use to finish the aesthetic/thematic elements, and some specific implementation solutions to performance and networking problems. We also hope that it'll reduce the amount of confusion around the game logic and entity setup required for the various TF game modes.
Our plan is to get more of our TF content source out in the SDK, so look for more maps & model sources in the future.
Read the Team Fortress blog