the easiest to learn i would think is bryce3d... as for the cool stuff i think most are using maya3d, or 3d stuido max... some that ive talked to are using rhino3d for the modiling... and yet others use lightwave...
______________ I'd like to put something witty here, but I'm just speechless.
to be honest, you're going to have to spend a good amount of time with any 3D program to get good at it. but to just learn, they're all fairly equal. cinema4d has the best interface that i've seen, but they'll all take a little getting used to. just choose one and take a good amount of time learning it.
rhino is a great interface to begin with. I had the easiest time learning how to model using it. It's much less popular than the others, but if you download flamingo as well, the renders look exponentially better.