Open Source Analog to Microsoft's Index Server?

An Anonymous Coward asks: "I have been tasked by my noble employer to find a better way accessing the 4,000 odd management documents and procedures we have. Currently MS Index Server is being used to provide a fairly good searching system. Index Server (for those that don't know) trawls through files and indexes their content.. ASP is then used to search the resulting database. My question is, there has to be a way to do this with nice open source software? Does anyone know of any competitors to index server that can index microsoft office documents? Thanks!" Might not HT://dig be a good foundation on which to build such a system?