Just wanted to chime in here...We bought a waist pack from this website and used it last weekend at Busch Gardens and Seaworld.
http://www.tuffbaggs.com/mm5/mercha...CBMITU&Product_Code=60g&Category_Code=WNHNFC7
At first glance, these bags look a little cheap, but ours really held up well and is even waterproof. And the prices are great...
We had 3 ponchos ($1 emergency kind), small tube of pain meds, small tube of dramamine, hand sanitizer, bandaids, package of pb & crackers, small fan, car key, and money in it and everything fit with room to spare. Hubby had the camera in his pocket and we just carried a bottle of water in hand. So, while this may not be ideal for those with smaller children who need diapers, wipes, extra clothes, etc., it worked great for us. And I didn't have to store it in a locker in order to ride the coasters. I know Disney pretty much lets you take your bags on any ride, but BG, SW, US, and IOA won't let you take any loose bags on the bigger rides. However, if you have a waist pack attached to your body, it's not considered loose!!!
Hope this helps...
-Melissa