A while ago Microsoft released some filter Webparts on MSDN.

SharePoint Filter Webparts including:
- BDC MultiFilter: Similar to the BDC Data Item Builder web part provided with MOSS 2007 Enterprise Edition, except it provides up to 4 additional filter connections containing BDC entity attributes to allow display of more entity-related data
- ShowFilter: Diagnostic display of any filter connected
- ShowFilterMap: Displays a Virtual Earth map when passed a filter containing a street address
- ShowFilterSearch: Displays MOSS search results when passed a filter connection containing a search query