SharePoint 2007 has some great search functionality so that majority of the popular files including Microsoft Word and Excel are setup to be indexed right out of the box. Want to learn how to extend the search engine so that it can index alternative files? This is where iFilter interface comes in to play:

The IFilter interface scans documents for text and properties (also called attributes). It extracts chunks of text from these documents, filtering out embedded formatting and retaining information about the position of the text. It also extracts chunks of values, which are properties of an entire document or of well-defined parts of a document. IFilter provides the foundation for building higher-level applications such as document indexers and application-independent viewers. [source: msdn]

The iFilter team has provided quite a few decent articles on how to index popular files:

• Indexing pdf documents with Adobe Reader v.8 and MOSS 2007
  The version 8 of the adobe reader has some significant architectural changes (for the better of course) including an inbuilt IFilter to index PDF documents. Previously the adobe IFilter was available as a seperate download. This new change in architecture…

• Indexing XPS documents with MOSS 2007
  With the XML Paper Specification (XPS) document format gaining popularity, many are wondering how to integrate MOSS 2007 to index and search XPS documents. Here’s a quick recipe to configure your index server to crawl and catalog tokens in XPS documents…
• Registering third party IFilters in WSS/MOSS 2007
  STEP 1: COM REGISTRATION 1.Add Registry key: HKEY_CLASSES_ROOT\CLSID\<ComClassIdOfTheIFIlter\InprocServer32 Default : <IFIlterDllPath> ThreadingModel : Both STEP 2 : REGISTER IFILTER WITH OS There are 4 steps to registering the filter-extension

There is another decent write up by Matt Groves on Installing and configuring the DWG iFilter from CAD & Company (beta1r2) - DWG files are AutoCAD file commonly used in the construction and manufacturing industries.

So why not check out these articles and see how you can provide better integrated search for files that SharePoint 2007 doesn’t index out of the box?