LEGO's official site seems a much better source:
https://wwwsecure.us.lego.com/en-us/service/buildinginstruct...
But what I like about it is that it has pretty good coverage of what is for me "classic" Lego. The official site in the parent looks like it only goes back into the 90s, and is missing a lot of sets.
EDIT: read too fast the first time. It does kind of look like the same set of scans for the linked site, although they have coverage for newer stuff as well.