Where do I get supplies for my project?

This is a great topic. I just responded to a question in the DIY section asking where to get pulleys and belts. These chinese engine kits are really nice and complete for builders who want to put something together quick and simple. A large percentage of this forum is made up of just that. But so many of us want much more out of a build. Especially the other catagories like Trikes, Boardtrackers, DIY, etc. I see so many different drive systems, like friction, belt, chain, steam, or combinations. How are you going to engineer something if you don't know what's available? Sure you can cut, weld, drill, tap, bend and grind on metel all day. Pulleys, sprockets, belts, chains, bearings and hardware are something not usually made in our home shops. I see a lot of guys putting something together with items supplied by Ace Hardware or Home Depot. If these same guys would just step into a place like McFaddendale Hardware or Industrial Metal Supply, I'm sure their jaw would drop from all the neat stuff carried by a real supplier to manufacturers and industry in general. I'll admit, I didn't research threads on this subject, but I think we would all welcome member input on different suppliers of fabricating supplies. Maybe a list to go in the Classic Instructions category.