Companies like Evermotion makes everything from material, textures to complete scenes, but when it comes to materials it is up to sites like, which are of very varying quality.
What I find surprising is that there isn't more of a market for the actual materials. Project Manager is very capable but somewhat lacking in documentation. There are a number of alternatives that are popping up such as Project Manager, Connecter, and I think iToo has something too or I may be mixing them up with someone else.
