I’m not being selfless here. I’m worried Google is going to drop this lovely service; they’ve already removed the Google Profile “My Library” integration. Some more traffic might help.
It goes like this:
- Search in Google Books.
- Select your book (for example).
- Click “Find this book in a library”. That takes you to the WorldCat entry for the book. (What is WorldCat?)
I don’t think you even have to create an account on WorldCat 
- Enter your zip code (it remembers the last entry) and browse the list. It showed the book in several local libraries. I clicked on the Saint Paul Public Library link and went immediately the request page.
Unfortunately I still had to use the silly Saint Paul Public Library authentication procedure. That’s the one where one enters a longish ID number that’s masked during entry.
It’s faster and much more elegant than going directly against our library system.
 You can export WorldCat cites to reference management software. That takes me back.