WWW.HALLOWEENHORRORNIGHTS.COM is the home website for both Orlando and Hollywood events. Keep checking the site for updates. Like Andrew mentioned, updates start ramping up during the summer.
You'll be able to buy tickets from the site, but don't get freaked out if you don't see Express Pass options right away. For some reason, they traditionally delay putting them up. So just keep checking back.
Cost per night creeps up every year and vary according to whether you're going during the weekend or on a weekday. We spent a little over a $1000.00 for a Saturday, a Sunday, and Halloween Night, but that's with the Express Pass figured in for each night. If you can plan around Fridays and Saturdays, you can save a lot on both the event ticket and the Express Passes, by opting for the Frequent Fear Pass Plus which gives you unlimited access Sunday to Thursday with the Express Pass built in. Universal tends to play around with ticket options, so there could be new wrinkles this coming year.
Hope you make it and have fun, it's a blast! :)
Walt Disney World's Magic Kingdom
Disney's Animal Kingdom
Disney's Hollywood Studios
Disney California Adventure
Universal Studios Florida
Universal's Islands of Adventure
Universal Studios Hollywood