The Search Jump user script provides a quick way to compare searches on various engines (or just to jump to another engine when the one you are using has poor results). It provides a small box at the bottom right of a search window, with links to the same search at other major search engines.
The current list of engines supported is:
It is also relatively easy to add support for new search engines by modifying the script itself.
If you encounter any problems, please let me know. Otherwise, enjoy!