I have bought alot from seedbay and seedboutique and have always been super satisfied.
The freebies are often totally awsome, I have gotten stuff like C99 and Blue Sattelite.
The regular store: https://www.seedboutique.com/store/
The auction site: https://www.seedbay.com/
Freebie forum thread: https://www.icmag.com/ic/showthread.php?t=32934

Vu-Du usually have the best selection of Mr Nice seeds, my favourite breeder.
http://www.vu-du.com/eshop/mainmenue.asp?ord=nome