I suffered from the worn bellcrank issue detailed by John earlier in this thread. Because the wear occurs so slowly, you may not notice when it's occurring.
I have a McLeod hydraulic T/O bearing and, as George mentioned, it significantly reduces pedal effort. Mine's been 100% reliable but others have found them to be a giant maintenance headache, so I hesitate to recommend them.
Years ago, in a P.I. magazine, there was an article by a guy who installed a Mitsubishi 3000GT power clutch booster in his Pantera. It worked just like a power brake booster. If I recall, he was installing a hand operated clutch mechanism and needed to decrease clutch effort by a significant amount. I don't recall the issue but someone else might. All I remember is, it was during the Adler era.