"The Encyclopedia Britannica states: 'There is no indication of the observance of the Easter festival in the New Testament or in the writings of the apostolic Fathers. The sanctity of special times was an idea absent from the minds of the first Christians.'"Here's a short but interesting article on various ways that Easter has been calculated throughout the centuries.
By the way, here's a neat Excel formula for calculating the date of Easter (western Christian tradition). I picked this up from J-Walk a while back.
I was born on Palm Sunday in 1964, and I had always been curious if my birthday would ever fall on Palm Sunday again. Using this formula, I found that the next time it happens will be 2054, so I will have to live to be 90 years old to see it. That would be cool.