Just saw this post by Scott Hanselman On the importance of OpenSearch, and I decided to try it out.

Took me no time at all to add it to WordPress!

Follow the instructions at Scott’s post for the most part – the only wrinkle is that in order to include the meta link, you’ll have to
1. go to Site Admin > Appearance > Editor
2. select Header (header.php) under Templates
3. look for other <link> tags and append it there

Try mine out! Go to your browser’s address bar (I tested w/ Chrome), type
philch [TAB] mvvm [ENTER]