http://www.microsoft.com/downloads/details.aspx?FamilyID=60c92a37-719c-4077-b5c6-cac34f4227cc&DisplayLang=en

This download will install and register IFilters with the Windows Indexing Service. These IFilters are used by Microsoft Search products to index the contents of specific document formats. This Filter Pack includes IFilters for the following formats: .docx, .docm, .pptx, .pptm, .xlsx, .xlsm, .xlsb, .zip, .one, .vdx, .vsd, .vss, .vst, .vdx, .vsx, and .vtx.

UPDATE[21.12.2007] - KB :How to register Microsoft Filter Pack with SharePoint Server 2007 and with Search Server 2008