rather liking the ESI Chunkys, soft without being too squishy. Good gloves might help too though (and make sure you take a few pairs, mine were rank after a couple of days, doesn't help at all)
Oh. And you know those Compeed heel blister plasters, the big thick ones? Those are absolutely brilliant for all manner of mtb blisters, they stay on better than anything else i've tried and they offer a nice thick pad too. I made the mistake of trying new gloves for the endurance dh race 2 years ago and had blisters the size of 50p pieces on each palm after 3 hours, these things saved my race... But also good for under pads etc, where normal plasters always fall off.