A great video showing the power of Excel and Web Services using Visual Studio 2008 and VSTO
(thanks Steven for the demo at the WSDF)
Links:
[1] http://pulse.veltsos.com/category/it/software/development
[2] http://pulse.veltsos.com/category/it/software/software/os/microsoft
[3] http://pulse.veltsos.com/category/it/office
[4] http://pulse.veltsos.com/category/it/web