At one of my regular hangout shops in Tokyo I found a huge box full of old manuals on sale for 10 yen a piece ($0.12)!
They were all Pentax and Minolta.
I grabbed several Pentax ones that related to the equipment I own. I already have a couple versions of the Spotmatic manual, the famous (just because of the back cover photo) 6x7 manual and a few others but these were new for me. I've found that Pentax made some of the best manuals. The spotmatic manuals are really informative and well written. You actually learn quite a bit about photography by reading them carefully. I don't know how the English translations were but the original stuff in Japanese is quite impressive.
Here's what I picked up today.
(In English!)
An older version of the same manual
A newer version