It is a day-long tour (like, 8:30AM-4PM) that covers onstage and backstage at EPCOT, Magic Kingdom, and Disney-MGM. Among the items on the tour... (highly subject to change depending on what's running and what isn't, the tour guide, the day of the week, whether the bus driver is lefthanded, etc)
Backstage at Catastrophe Canyon
Backstage inside American Adventure
Backstate around World Showcase
Backstage behind Living Seas, Test Track, The Land, and other EPCOT attractions.
Backstage inside the costume manufacturing department
Backstage inside the wardrobe checkin/checkout department at EPCOT
Backstage inside the main shop, where they make ride vehicles and AudioAnimatronics
Backstage underneath the Magic Kingdom (Utilidors!)
Backstage inside Holiday Services (where they store all the Christmas decorations for the entire park/resort/cruiseline chain).
Also includes some limited onstage time (mainly for lunch at Mama Melrose's, which is included in the price of the tour). The tour hovers around $200 (and does NOT require a separate park admission fee), but I believe it is well worth it! If you're a true Disney fan, you'll really love pulling the curtain back. You must be 16 years old (with photo ID) for the tour. No cameras, big bags, bazookas, etc.
If that's a little out of your range, I might suggest Keys to the Kingdom. It is similar, in that it offers some backstage peeks, but also has much more onstage time. You'll probably ride a few attractions on that one. The key difference is that Keys only covers the Magic Kingdom. It's around $50, plus you ALSO have to pay admission to MK. Your lunch is included, but it's quick-serve stuff like Columbia Harbor House, rather than table service like Backstage Magic. You must be 16 years old (with photo ID) for the tour. No cameras, big bags, corporate espionage utensils, etc. I'm taking Keys at the end of the month -- hope it's good. Good luck planning your trip!