Well, the place I go to, you get no money, no matter what. the preimums, like t-shirts, frequent flier miles and such are fun, but you never know what you'll get when you come in.

Other places will give money for whole blood or plasma... I'm not sure how the cost splits out, but I think you get a better bang for your buck with plasma, because you can give that every 2 weeks, rather than 8 with whole blood.