I have recently become familiar with Add-ons. On Firefox, add-ons are toolbars from sites that provide direct links to the site and more. I have the De.lic.ious add-on. The add-on allows me to bookmark sites, tag sites, and view my bookmarks in several ways (most visited, newest…). A music add-on that I have can provide radio and free music downloads from the site.
I think it would be very interesting, and extremely convenient for libraries to provide add-ons. They could have a search bar that links to the catalog. An “Aways logged in” option that will also let the patron know when their holds are in or their books are overdue or even will be due soon. There could be a “Ask the librarian” button that will send the user to the Ask24/7 form to ask reference questions. A link to the library blog. A “daily events” tab or dropdown menu. There are endless possibilities.