American Science & Surplus
This website is a tinkerer's delight. One legendary source of cheap parts, weird stuff, cheap knockoffs, and plain junk is American Science & Surplus. They sell "closeouts, inventory overruns, mis-manufactures, and items whose time has not come. When a surplus item is gone, it is gone." It's the ultimate hacker's mail-order junk store.
They don't take themselves too seriously, either, often belittling the scrap they are selling. The items are illustrated with crude sketches on yellow newsprint paper in their crowded 95-page paper catalog. It's a cornucopia of irresistible bargains. Science fair motors! Chemistry kits! Craft tools. I dare you to open it without finding something you have to have. In addition to the doodles, you can click to see a photo of an item as well.) While funny, their descriptions are always honest, and the stuff delivered will be entirely useable. More so than most catalogs, the bulk of the items listed are inspirational: " Oh, I could do that!" Prices are, as they say, incredible.
Click this link to visit American Science & Surplus: http://www.sciplus.com.