From the Official Disney Parks Blog…
The Happiest Place on Earth is about to get happier – and beginning with arrivals on June 18, 2012, guests staying at a Disneyland Resort hotel can take advantage of Extra Magic Hour* – early admission to either Disneyland park or Disney California Adventure park – every day of their stay (with valid theme park admission and active hotel room key card).
Extra Magic Hour will allow registered Disneyland Resort hotel guests admission into select attractions at Disneyland park on Sunday, Tuesday, Thursday and Saturday and Disney California Adventure park on Monday, Wednesday and Friday, before that park opens to the general public.