These days: Dream (highly unprofessional / suspicious), Libertas, CGMC (only cannabis & psychedelics, extremely well done), and Zion (up and down due to DDOS).

These days: Dream (highly unprofessional / suspicious), Libertas, CGMC (only cannabis & psychedelics, extremely well done), and Zion (up and down due to DDOS). The last one at the very least support Monero, but I believe it's not the only one. That list is only a list of the "true" markets; there are also numerous forum-based ones. A lot of the above also handle multisig (including monero multisig), to make sure a vendor can get his coins even if the market disappears. There's also a galaxy of small websites / forums opened by single vendors themselves, in order to sell directly.