If you look through the various pages under this directory, you'll find a lot of information about fabricating plastic/metal/etc parts from a hobbyist/DIY/home perspective.

This page summarizes various manufacturing techniques that work well for DIY purposes, across all mediums.

As with every list on this website, items near the top (or left) are ones I find more valuable. (though, of course, my goals may be different from yours)

plastics

metal