Microsoft Search Server (MSS) is an enterprise search platform from Microsoft. Microsoft Search Server Express is based on technology from Sharepoint and can compare to Google Mini Search Appliance, however MSSE is free with very few limitations (only one I know of is Clustering). Via it's really userfriendly Sharepoint like interface you get full control over sources to crawl and index - both local files and external websites.

Powerful enough to meet your search needs now and as they grow. For customers just getting started with search, Search Server 2010 Express is a standalone search server that is free to download and easy to deploy. It incorporates many enhancements over its predecessor, Search Server 2008 Express.

Microsoft Search Server offers a familiar search experience, empowering your people to connect with your organisation's existing information and business systems. Search Server 2008 helps you build an enterprise-class search infrastructure that provides the right balance of control and simplicity.

The license of this software is Freeware, you can free download and free use this information management software.