For an exhaustive list of events beyond those listed here, check http://events.frommers.com, where you'll find a searchable, up-to-the-minute roster of what's happening in not only Orlando, but in cities all over the world.
Halloween Horror Nights. Universal Orlando's Islands of Adventure (tel. 888/389-4783 or 407/363-8000; www.universalorlando.com) transforms its grounds on select nights during October and into November into haunted attractions. Live entertainment and special shows, hundreds of ghouls and goblins roaming the streets, and specially designed haunted houses make for a truly terrifying experience. The park essentially closes at dusk, reopening in a new macabre form from 7pm to midnight or later. Full admission ($85 adults) is charged for this event, which is definitely geared to grown-ups (as the liquor flows freely and the frightfulness is truly that). Note that guests are not permitted to wear costumes (so that Universal employees can spot their peers).
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.