You get a choice between the 3 Skypephone or the new Nokia 3120, in black. It's a simple phone, and has a 2 Megapixel camera too, on a 6 month contract for £15 p/m. You get 300 mins/text anytime any network on mix and match tariff, plus 300 FREE mins from 3 to 3.
If you know anyone already on 3, you can tell 3 that they recommended you and both you and them will receive £30 off your bills after 60 days through RAF scheme.
Over 6 months, that comes to £57.50 after Quidco and £27.50 after your RAF discount. And your friend gets £30 off their bill too!
If you wish to keep an existing 3 phone, you can sell either of the 2 ~£40 on eBay.