Look here:
http://www.ctc.org.uk/DesktopDefault.aspx?TabID=3946
There aren't any combos that will work for S8 cassette using C8 shifters. You could use C10 shifters with a Shimano RD or a C9 (new) shifter with a Shimano RD (alt. cable routing). Otherwise you may have to use a shiftmate, or you might be out of luck.
Or, if you find an Pre-2001 Campy RD, give it a shot. For some people if shifts acceptably well just like that. I've never tried it.