Valve's Source Filmmaker has now added Steam Workshop support, meaning that community will be able to easily share assets in a fully peer-to-peer environment.
Sounds and models are two of the most frequently requested features, and have now been added, but Valve warns: "the first time we hear a solid impression of Dr. Kleiner singing Baby Got Back, we at Valve will all collectively lose it."
More details, and the first batch of assets to be uploaded, can be found here.