A large collection of Mechanical / Electrical / Tech parts. I've been modeling Sci Fi vehicles for about a year now, and I've ended up with some nifty parts. Might as well share them with you guys... hopefully it will save you a little work.
In anyone's interested, you can also vote on my future BlendSwap projects here.
EDIT: The blend contains a "Chain Builder" tool with a narrative description (Text Object). The description tells you to scale the chain, but this is not correct. Use the array modifier to add/subtract chain segments instead. I don't think it's worth re-uploading a 12MB file to fix this... just wanted to mention it.