Kermit - Should be fairly easy to pick up on eBay, he was one of the first figures
Fozzie - 4 versions are available as of now, San Diego CC exclusive Invisible Spray Fozzie, Toy Fare Exclusive Red Shirt Vacation Fozzie, Best Buy Inc (Media Play, Sam Goody, Suncoast) Exclusive Blue Shirt Vacation Fozzie, and regular Fozzie
Crazy Harry - Might want to check ebworld.com or beanstoys.com (same for Kermit, Miss Piggy, Gonzo and Fozzie)
Miss Piggy - 2 versions available, regular Series 1 and EB exclusive purple dress Piggy
Gonzo - 2 versions available now, regular version, and EB (I think) exclusive repaint, Series 5 will see Gonzo in purple tux with Camilla
Animal - 2 versions available, 1 exclusive to the Electric Mayhem set, the other exclusive to the Palisades Convention Tour (wearing a Palisades tshirt)