The OpenSearch Toolkit provides ASP.NET developers with drop-in support for OpenSearch. This lets you quickly and easily publish valid search suggestions to all the major browsers.
Traditionally, complete OpenSearch support has been hard to achieve. You need to publish a valid description, an XML feed for IE8, a JSON feed for Firefox and an RSS feed with custom extensions for Windows 7 Federated Search. Each of these formats are defined under different standards maintained across multiple organisations. This complexity inspired the OpenSearch Toolkit, and the accompanying OpenSearch Validator
(also on CodePlex
For implementation guidelines and screenshots, see http://blog.tatham.oddie.com.au/2009/07/19/announcing-opensearch-on-asp-net-made-super-easy-with-the-opensearch-toolkit/