OpenSearchForSafari (http://www.opensearchforsafari.com/) has been updated and is compatible with the version 5.1 release of the Apple web browser.
The extension implements the OpenSearch technology into Safari. With OpenSearchForSafari, you can search on Wikipedia, Amazon, in the iTunes store, on Flickr or Engadget with one single click on the toolbar item or shortcut (Option + Command + O) right in Safari and without leaving the current tab or page.
The extension provides language support for English, German, Spanish, French and Italian and comes with predefined local plug-ins. It’s compatible with Mac OS X 10.6.8 and higher.