Search Keys extension for Firefox

Search Keys lets you go to search results by pressing the number of the search result instead of clicking. For example, pressing 1 takes you to the first result. Hold Alt (Windows/Mac) or Ctrl (Linux) to open results in new tabs, or Shift to open results in new windows.
Search Keys supports Google, Google Image Search,Google News search, Google Local, Google Groups, Google Desktop Search, Yahoo!, Yahoo! Image Search,Yahoo! News search, Yahoo! Local, Yahoo! Personals, and del.icio.us.

Following is screenshot(click to enlarge):