MutualPoints is the easy peasy one.
Recommend you use a different email address (I have a Yahoo address just for this) as you do get a lot of mails. Choose to be paid in points and register for Reward Mails.
You get emails with clickable links. The points rewarded vary depending on if you take up offers or not, but you usually get 5 points just for clicking a link.
Have a look around the home page. There is loads of stuff you can sign up for (email newsletters and the like - hence my reasoning for a different email addy!). It is also an online shopping portal - if you use their link to an online supplier you get mutual points.
You do need a lot of points to cash in (3000 = £20) but it is easy money.