Neocities.org

I use AliExpress for components that are difficult to screw up or for non-critical things. It's great to have a lot of spare components and assortment kits on hand.

For important projects, I usually go through Mouser or Digikey. I often use Ebay as well, if it is something rare enough or I need/want old-stock. In my area there are many clearinghouse/surplus stores that sell a bunch of old electrical components.