PopSearch Safari Extension

PopSearch Safari Extension lets you easily add any search engine you like to Safari. If you use Safari 6, you can even access your custom search engines right in the combined address/search bar by typing short keywords like "w" for Wikipedia before your search terms. Otherwise, simply use the convenient popup search bar by typing Command-K or another hotkey of your choosing.
Features: It's easy to add other search engines to the built-in ones.