The Search Engine Decoder is a tool that displays the relationships of various major search engines. Use this tool to see which search engine supplies and receives its primary and secondary search results, directory search results and paid results to and from which other search engines.

You can also display ownership relations and the Nielsen Netratings (percentage of all web searches) for each search engine.

Quick Lookup is a nice new tool for Web developers based on AJAX technologies. It offers a tabbed search interface that lets users currently choose between PHP, MySQL, JavaScript, and CSS. Search is performed while typing. The results display quick reference information for functions, methods, classes, attributes, etc. For more in-depth information there is also a link to the documentation source. A great idea. Give it a try.

GrayBit offers a tool for converting the colors of your website to their grayscale equivalents, so you can test the visual contrast of your website. Like most other Web 2.0 application GrayBit has it's limitations and works best on websites that make use of cascading style sheets and a standardized markup. Nonetheless it's well worth trying this on your website as an additional tool to test this aspect of accessibility.