I have just been paid by RNS Topfuel. They pay 1 cent per email that they send. You have to click through the link in that email and then do a search on the search engine that appears.
I use to get about 50 emails a date hence my payment this month of £4.21. (They pay in dollars to Paypal). Lately I have not ben receiving many emails from then but it seems, from the emails I have been getting from the admin, that this is a temporary glitch.