There are actually a couple of different types of italian charms available. There are the stainless charms that run about $25 apiece, the single dangler charms run about $45, the double dangler charms run about $60. If you just want to quickly fill your bracelet, there are also a metal charm that is $3. The choices are pretty limited: Mickey, Minnie, Pooh, Tigger, Eeyore, Belle, Cinderella, Sleeping Beauty, Tinker Bell, jewelled Mickey heads that lose their stones quite easily (I broke lost 2 stones in 2 different charms in 3 months and my friend lost 2 in 2 charms in the same amount of time)
Most of the larger stores have them in the display cases. World of Disney has the book you can look through as well. They are actually very easy to find and you can decide if you want to get all the expensive charms or start with the cheaper ones and work your way up to the expensive ones.
The website
www.dollsandducks.com has roughly the same selection that they have in the parks, but if you have an AP, you can use your 10% discount at World of Disney and get them a little cheaper!