Seek and you will find

Autodesk's Seek Site is a great resource for finding not only Revit families and components, but also other files formats.

I have been putting together some families to post to the Seek site for Autodesk. I've been impressed on how stringent their policy is for how the family is built, the parameters within the family and overall consistancy of what is available for users to download for free. Its a great resource for finding most everything you need to pull into your project. And if its not there, you can suggest to a manufacturer to have it built. The best thing is to just go search around for a little while and see for yourself whats out there. Here is the link, enjoy! http://seek.autodesk.com/