People who practice something descended from Scientology without being in the Church of Scientology are generally collectively referred to as the Free Zone, though not all of them like the term. Some are weirdly sci-fi-ish, a lot are near the weird end of New Age. Some are very Scientological (including belief in Xenu), some you'd barely know were related. In general, they're much better-behaved and much nicer people than the Church of Scientology, though that's not hard.

The only one I know of that has any sort of acceptance as non-lunacy in general circles is Traumatic Incident Reduction, an abreaction-based psychotherapy derived from Dianetics by Frank A. Gerbode, an ex-Scientologist who went on to become a psychiatrist. (Hubbard started off pitching Dianetics to psychiatrists, and was greatly embittered by them dismissing him as a crank.) It isn't particularly noteworthy and I don't know of any clinical trials of it.