Chiming in late, but I found that a lot of the specialized boards and gadgets on ebay and AliExpress, things like the AVR transistor tester clones, USB testers, and more interesting little modules originate from small builders that have their own TaoBao shops.
I got pretty good at finding the shops by careful inspection of photos, google translate, google searches, and image searches. Having done so, I found even more stuff well before it showed up in listings on ebay. For example, I got some automated battery testers I found there by way of Franky long before they ever showed up on ebay, for less than they were selling on AliExpress (which didn't ship to my state at the time anyway).
More recently, I've tracked down some interesting modules on TaoBao that aren't available on AliExpress or Ebay.