I have NOT tried this myself, just thought it may be of interest to some of you guys.
From their Website.
Samba was founded in the UK in 2009.
We work with mobile networks and the advertising community to provide free access for people to use the internet when they want.
Users build their mobile broadband credit by selecting and viewing high quality advertising.
Nobody has ever offered something like Samba before, so if you want free mobile broadband, just sign up, and we will send you an exclusive invitation when a space appears.
Samba is founded by accomplished internet, mobile and advertising entrepreneurs from Orange, Digicel and Media Edge:CIA. It is funded by Irish telecoms entrepreneur Denis O'Brien.
[Only registered and activated users can see links. ]