Microsoft have released Download details: Microsoft Filter Pack. This provides iFilters for the new Office 2007 document formats. From the download page:

"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.

Because Windows Desktop Search (WDS) consumes IFilters from Windows Indexing Service, the IFilters will be automatically registered and available for use by WDS.

To register these IFilters with a specific Search product, please see the associated KB article below:
Office SharePoint Server 2007 - [Office SharePoint Server 2007 registration steps
Search Server 2008 - Search Server 2008 registration steps
SharePoint Portal Server 2003 - SharePoint Portal Server 2003 registration steps
Windows SharePoint Services v3.0 - Windows SharePoint Services v3.0 registration steps
Exchange Server 2007 - Exchange Server 2007 registration steps
SQL Server 2005 - SQL Server 2005 registration steps
SQL Server 2008 - SQL Server 2008 registration steps"

NOTE: If you use Windows Desktop Search or Windows Search with one of the server listed above you probably want to install these filters.