Rio 1 & 2 Blu-Ray boxset for pre-order at Amazon, only £13. Rio 2 pre-order is £15 so this is £2 cheaper with the first film chucked in for good measure!
(The first film is also £7.05 at the moment, so if you bought both separately it'd be £22.05 - this boxset shaves nearly £10 off that, plus free delivery as it's over £10!)
Not sure how long this will be this price, it's out on 4th August. I pre-ordered the Need For Speed 3D Blu-Ray a while back when it was £13 (same as regular version) then it went up to £15 a few days later so it could go up soon.
First time I've posted a deal - think this is the right sort of thing to 'alert' people too... ;)
EDIT - Forgot to mention, Rio 2 comes with DigitalHD Ultraviolet copy too!