Some clusters that seem related but not much discussed on LW:

• The "aspiring Mentat" cluster, which includes the entire mnemonics subculture, various brain-training groups, the mental math subculture, and some parts of the magic tricks / mentalism subculture and professional gambling subculture. Some weirder parts are the lucid dreaming groups, the hypnosis groups, and the tulpamancy groups. Slightly overlapping subcultures are those around various games, e.g. chess and speed-solving of Rubik's cubes. For an example, see the book Mind Performance Hacks, or the Mentat Wiki. This overlaps with some very obscure Russian inventions, such as the TRIZ system of innovation, the theory of "psychonetics", and the Trachtenberg system of speed mathematics. There's also some overlaps with conlang subculture, such as Ithkuil and Lojban.

• The "aspiring Ubermenschen" cluster. Some names that come to mind as prototypical: Tim Ferriss, Jason Shen, Sebastian Marshall. This is a part of the larger productivity culture, which includes e.g. Cal Newport, the GTD people, etc. They tend to monetize their writings, for obvious reasons. There's a spectrum here from the saner groups to the more woo-ful, e.g. Steve Pavlina. This overlaps with a "drugs for self-improvement" subculture, which includes various nootropics groups, and parts of the steroid subculture. Also overlaps with the self-tracking / quantified self subculture.

• The "outlandish schemes to improve the world" cluster, which includes e.g. Esperanto, veg*anism, the writings of Buckminster Fuller, various anti-nationalism movements, etc. (Veg*anism definitely correlates with Esperanto, for instance. Of course, a lot of veg*ans don't engage in the rest of this cluster.) Overlaps with more woo-ish things like various forms of non-theistic spirituality.

Some others:

• The psychoactive drug subculture.

• The cypherpunk subculture. "Hacker" culture in general is very close to LW memespace.

• The manosphere.

Also groups associated with various professions, such as tech people, econ people, and math people.

It may be worth clarifying that "cluster" here is (I take it) intended to have roughly the same meaning as in the old OB post The correct contrarian cluster, meaning something like "set of somewhat-related ideas". So mushroom is, I think, asking whether there are ways of looking at the world, or (so to speak) toolboxes for thinking, that aren't already familiar to most of the LW readership but might be useful.

(mushroom, please correct me if I've got it wrong.)

I seem to be missing some context for this. Taboo cluster?

What do you mean? Topics of interest to this community that have not been talked about yet?