These guys are taking PhD's in Chem/Bio/Comp Sci/Econ/Math.
U.S. students post problems, and name a price they are willing to pay.
Then if you (a PhD) see a problem you are capable of helping them with - you solve it, and you get paid to do so!
www.brainbuy.org
We are given 2/3rds of the amount the student pays! Profits go to charity!
They'll send you a login/pass to view questions. Next you login, view questions, post solutions and they will have cheques sent toyou IF YOU ARE IN INDIA.
Dinesh