Family of 4: £330.00/year
Individual: £110.00/year (or £27.50 in Tesco Clubcard Vouchers - thanks karri123)
Apologies if this has been posted before - a quick search didn't reveal anything. This seems like good value for families that will visit a number of the attractions listed in a year (and you would have to visit several for this to be good value for money).
Read the FAQ at http://www.annual-pass.com/faq/faq.asp?css=1
Includes entry to Alton Towers Resort, LEGOLAND® Windsor, THORPE PARK, Chessington World of Adventure & Zoo, Madame Tussauds London, SEA LIFE Centres & Sanctuaries, Warwick Castle and The London Eye.