Search Craig's list real time application for Mozilla's Firefox browser.
Search Craig's list resultsThere are a number of other search engines that have apps that can be added to the drop down menu box under the search engines box upper right of the screen.
Google Books
ThomasNet Industrial search (equipment,materials and who does stuff)
World cat (world wide library book search)
Item look up (ISBN/UPC/EAN Barcode Number.)
Amazon.com
And 100's of others, they also have country specific search engines for Mozilla Firefox's browser. They probably have them for other browsers as well.
As I only use firefox I have no info on them.
For those that may not know, An add-on can be a new time-saving toolbar button, a shortcut to search, a themed look, and more. Add-ons make browsing easier.
This is the link to the English/US versionThey have other sites with other languages