With Samba Mobile, you pay a one-off £2.50 to buy the SIM card (usually £5 but the attached link has a half price discount) and when you receive it you can get free 3g mobile internet (eg. for your laptop or tablet). This is ad supported, so you just need to watch a few ads to build up your data. You get 3.5 megabytes of data per ad so for general internet browsing you don't need to watch ads too often. Plus, you don't really have to actually watch the ads, just click play and turn the sound off and you can carry on with whatever else you're doing on the computer while the ad is playing.

That's it! Unless you opt to pay for more data you can get permanently free internet!

I don't think the dongle is included so if you need one of these you will have to order it separately (obviously if you're using in a 3g enabled tablet you won't need one of these).