Tsukuba is a great one, and usually the go-to drift course for most people (including myself).
I do like to toss it up with a little variety here and there, so some other tracks that I enjoy drifting are:
Indy Road Course - Nice and flat with some technical sections.
Trial Mountain - Fun elevation changes, great chicanes.
Top Gear Test Track - It's fantastic in an open lobby if you are with a good group of people.
Cape Ring - Any configuration works, but I usually skip Periphery if I'm looking for drift-only. Can you hold one for the entire helix?
Laguna Seca - Epic. Even if you're like me and not very good at drifting.
I highly recommend trying as many different cars as you can. One of my fave's is the RUF "Yellowbird." It slides even when you're trying to go straight!