I can get credit for my prepaid mobile. $10 recharge usually last me at least one month since I don't use up too much credit on my mobile. Might not work for you, I know; especially if you don't use prepaid mobile...
There are a lot of things you can buy online with ten dollars. Check out ebay or amazon and look for free shipping.
There are a lot of e books online if you are interested in books.
You didn't say what you are interested in so this is a random answer.