Alright, here's one...

Sculpture Supply Canada: <!-- m --><a class="postlink" href="http://www.sculpturesupply.com/">http://www.sculpturesupply.com/</a><!-- m -->

Hydracal and casting plaster are sold in 50lb bags. Way cheaper than the little boxes you get from WS in the hobby shops.

They've also got RTV Rubber for making molds and gallons of resin for casting your own parts.

Not to mention plaster bandages by the case!

For the folks in the Los Angeles area or Las Vegas, Nevada there is Aardvark clay & supply. <!-- w --><a class="postlink" href="http://www.aardvarkclay.com">www.aardvarkclay.com</a><!-- w -->