Microsoft's Enterprise Search include several options:
- Microsoft Search Server 2008 Express
- Microsoft Search Server 2008
- Microsoft Office SharePoint Server 2007
- FAST Enterprise Search Platform (ESP)
Microsoft Search Server 2008 Express, or MSSX, is a free entry-level solution designed for situations (e.g., departmental search) where a single server for both index and query will meet your needs.
Microsoft Search Server 2008, or MSS, is an entry-level solution that can be scaled across multiple index and query servers. We recommend it as a basic solution for organizations who don't have Microsoft Office SharePoint Server deployed, but who have many users who need to crawl large volumes of data.
Microsoft Office SharePoint Server 2007, or MOSS, integrates all of MSS's features and adds to them SharePoint capabilities such as the Business Data Catalog, which allows for searches against structured data stores (e.g., line-of-business systems like ERP or CRM).
FAST Enterprise Search Platform, or ESP, provides best-in-class enterprise search solutions. FAST ESP provides a scalable, robust, and highly tunable search platform for the most demanding requirements and most tailored user experiences inside or outside the firewall.