My partner has found viewing PDF workshop manuals on the iPad (via Goodreader) invaluable while working on one of our cars. He is accessorizing it, and has made minor repairs. and pinching-and-zooming into blown-up diagrams of parts and wiring is, to use his word, "fantastic!". We've tried to get every manual for everything we have into a shared Dropbox folder for this purpose.
Sorry I can't help you with locating workshop manuals. Any searches I have done have always been fairly random. Forums dedicated to your particular brand of device/machinery are often a good place to follow and seek advice, as they've often a lot of folk "hacking" the thing in the absence of, or the presence of, said manuals (or their own derivatives).