This is a comprehensive directory. It misses some casinos, but lists most of the large ones.
http://www.winneronline.com/casinos/
I also agree that listing most online casinos is not a good idea. Especially considering half of them probably dont even pay players.
From a players perspective they want a portal to know which casino is worthy of thier time and money. If they wanted to find every online casino out there they could just search ‘casino’ on google.
Antoine