VicinitySearch is a WordPress plugin that allows a search request on your local Weblog to transcend the borders of your blog into its semantic vicinity.

WordPress exposes a search function, which lets readers search a blog for certain search terms. Wouldnt it be nice to search for a term in the semantic vicinity of a Weblog?The VicinitySearch WordPress plugin does exactly that.It allows asearch requestto continue along all blogroll links which also use the vicinitySearch plugin or any compatible vicinitySearch XML-RPC service provider. If you want to see vicinitySearch in action, just search on this Weblog, search request will automatically transcend to my Blogroll links Photoclub Lampaden and the CrePes Weblog.

In order to make use of vicinitySearch-enabled Blogs or websites among your blogroll links, you will have to set up theURL of the vicinitySearch service provider in the Links > vicinitySearch configuration menu. The plugin also automatically installs a vicinitySearch provider for your blog, which can be used by Weblog administrators linking to your Blog. In order to find out the URL of your own vicinitySearch provider, just have a look at the source code of your Weblog.You will find alink rel tag in the head sectiononce the plugin has been activated. This tag can also be used by developers in order to automatically check whether a Weblog uses vicinitySearch.

[via, Download the vicinitySearch Plugin for WordPress 2.x ]