HTC Desire on Vodafone 12 month contract! Quite rare to find a good deal on these "short" contracts!
£45 per month with a free handset. For this you get 900 minutes and unlimited texts.
Mobiles.co.uk are offering 4 months line rental 1/2 price taking the total price from £540 to £450.
Go via quidco for an additional £50 cashback taking the total to £400 or £33 per month!
Edit - You can add internet for £5 per month, so making the total £460 or £38 a month. Personally I think this is still a good price for a 12 month contract. To buy the phone sim free from Amazon would cost £439. Every where else seems a similar price.