To go in a different direction from the other posters — as there is no such thing as an actual "thunderbolt hub", and the OP specifically mentioned USB-3 ports, I'd like to throw in a mention of a really excellent
USB-C hub (!) that I've been using for the last few weeks:
Juiced Systems VertexHUB
It takes one upstream USB-C 10Gbps port, and provides
four full-speed 10Gbps-capable USB-C ports
as well as three superspeed USB-A ports on the back, also 10Gbps. It's also got a dedicated power-brick, and thus can power high-speed spinny drives and whatnot.
The advantages here over the CalDigit (which I also have, but for a completely unrelated reason) being 1. cheaper, 2. more USB-C ports, 3. more 10Gbps ports (the CalDigit only has one, the rest are 5Gbps), and a smaller form-factor if you don't need all the additional functionality of the CalDigit.
The build-quality is also unparalleled; and since it's USB-C, not Thunderbolt, you can place it more than 2 meters away from your Mac Pro, lol. (I'm using
this active cable, run upstream to the Mac Pro in my rack.)