PopSearch gives you two ways to use your custom search engines. If you use Safari 6, you can access them right in the browser’s combined address/search bar by typing a short keyword (like “w” for Wikipedia) before your search terms. Also, you can change the default address bar search engine to one of your custom ones.

In either Safari 6 or Safari 5, you can use PopSearch’s own convenient popup search bar by typing ⌘K (or another hotkey of your choosing). You can select the search engine using either keywords or a drop-down menu.

PopSearch comes with a few predefined search engines, but it’s easy to add your own. Just click the Settings button on the popup search bar and enter a search URL template. Or let PopSearch automatically create and add a search template for you by using its Engine Wizard on a search results page.

Requirements:
OS X 10.5.8+
Safari 5.0.1+
Intel