Quite a bit of the late 80's early 90's part diagrams are not up, there are a few other places a well, but don't have the links handy. EDIT/ do now see below/
They are often found by typing in the full part name and hitting images (in google search), e.g. BR-M735, RD-M910
Also you'll find some nice ones, that are good for posting in forums as well, here http://www3.big.or.jp/~number-1/No.1_ShimanoRP.html
Navigation can be interesting, but you'll soon get used to ist and reading the status bar for where a link is going. Also Chrome can now sort of translate some of it