Here's one that has some well-known pieces...
http://balladora.blogspot.com/2007/03/wolfgang-weingart-works.html

MoMA has some, too:
http://moma.org/collection/browse_results.php?criteria=O%3AAD%3AE%3A6289...

The rest of these links contain more text than images, I'm afraid...

http://www.weingartarchive.com/

http://www.the-artists.org/ArtistView.cfm?id=37A0AAE0-F88D-EE73-59EF20FF...

James, I presume you're within reach of a library? Because you could always go and borrow his book...

There's also quite a lot of Weingart in person in Kathryn Cho's documentary movie 'Typecast'. But I understand it's the work you're looking for, rather than the man.

The library in my town stinks, it's got nothing in terms of design. . . But I'll buy it some time soon. Thanks for the input guys.

Actually it's not about what is currently on their shelves – but what they can borrow from other libraries on your behalf. You need to find out about inter library loan (ILL) http://typophile.com/node/31868