I've used both adf.ly and zpag.es, adf.ly is better for the publishers but zpag.es is far better for the users who click the links. Far less annoying - you wait 5 seconds rather than waiting for the whole page to load before the 5 second count (like on adf.ly)... so more likely people want to click the link.

P.S. but adf.ly wins because zpag.es payment is EXTREMELY slow