Collector Sites
The best sites for rubber duck collectors is duck Planet. It has a nice well moderated forum were collectors can discuss the hobby. It is owned by Charlotte Lee the owner of the Guinness World Record duckie collection.
Another cool duck site is Duckshow. It is a photo blog about many ducky things. It is run by Colleen one of the coolest duck collectors.
Cool fun site and home of Rodger the travling duck.
Buying Sites
Pricehot
Oriental Trading Company
Ducks Only and there sister site Buck A Duck
ebay
Current Duck Makers Sites
CelebriDucks
BUD Ducks
Rubba Ducks Links not working the day I added the link