If you're on a web page that displays a book with its ISBN/ISSN number, you can search or reserve the book at our local library with one click using this bookmarklet:
Now, whenever you're on a web page showing a book you want, just click the "Peninsual Library System" link on your toolbar. If there's an ISBN/ISSN number on the web page, then a new window will open with the search results for that book in our local library. The search includes all these San Francisco Peninsula libraries. You can then reserve the book online and pick it up at your local library.
If you're not my Mom, and want a bookmarklet for a different library system, check out The LibraryLookup Project.
Update: the link now looks for the ISBN/ISSN on the web page itself if no number was found in the URL. So clicking the link from step 1 above should now jump to the Barack Obama best seller because "ISBN: 0307237699" is on this page.