Here are some ideas that work:
1. Freelancing - if you have some computer skills or have expertize in some area.
2. Online auctions - you can always sell something (sometimes even bizar stuff can make a lot of money to the person who sells).
3. Online store - if you have your own products and services (if you don't try to find someone who needs a resseler or dealer).
4. Commisions and refferals - this could be hendy because you'll work nothing and money comes (be carefull not every site pays).
5. Pay per click (most of them are scum and never pays, some would dissaper in week so be carefull), still there are few who work correctly.
I hope this will help. You'll have to research by yourself. If I tell you, you should become my reffered member

so I'll make a money by your joining. (Isn't it a way of explotation?

)