Anything other than signature campaigns and gambling.
A bit saved is a bit earned. So save your money by not clicking on any of the signatures of the people posting in this thread.
Mining is good. Just invest on a pc with multiple graphics cards and you're on your way. The more cards, the merrier the mining rig. You just have to watch out for the electricity bills and the heat dissipation coming out from these cards. Sell the components after you made your buck.