Shaun Inman has released Shortwave, an “extensible quick-search and shortcut system” in the form of a browser bookmarklet with a hosted JavaScript file.
Rather than passing search items though a domain that he didn’t control, Dominic Szablewski has created (and caused some controversy) QuickSearch.js with similar functionality but allows you to host the JavaScript on your web space.
WordPress Waves
In testing out Shortwave, I built some WordPress specific shortcuts for my custom waves.txt file. The added shortcuts are a WordPress plugin search, a WordPress Codex search, and a search of my site.
wpp http://wordpress.org/extend/plugins/search.php?q=%s WordPress Plugin Search
cdx http://wordpress.org/search/%s WordPress Codex Search
ww http://iamww.com/index.php?s=%s IAMWW Search
Others Sharing
Sam Brown has also posted his wave file with custom shortcuts including a including Google UK Search.