Knee Deep Productions presents Whistler Guide Books
these books are really excellent - there's an advanced one and an intermediate one, buy them early, they are fun to read and I find that they really get you stoked for a trip
an earlier poster made an excellent point, as did a friend of mine who is local - you can get a lot of great laps in before the high alpine opens, don't waste that time, if the high alpine is closed it's probably because it snowed and mid moutain there will be lots of good runs to be had
also there's a whistler app for iphone/ipad, very handy, shows what lifts are open, grooming conditions and other stuff. Like Clarion I look at it every day before work here in Toronto.