I had a Wheels manufacturing inc. cassette called 'the accelerator' which allows you to use a shimano/sram spine pattern freehub with campag kit. It is basically an Ultegra cassette with machined down spacers to campag spacing, you use a campag rear mech, chain and ergos and it works perfectly. They aren't cheap, approx $180 but very good quality, I sold mine on ebay recently for about £35!
Otherwise I find it's a bit hit and miss mixing campag and shimano kit, I've had some rigs that worked a treat and some that were dogs.