Since the StackExchange sites are webapps, it seems like Web Applications should be the one site that doesn't have a Meta. In other words, right now you can ask questions about all the web applications out there on Web Applications except for StackExchange.
For Example: You might want to ask
How do I insert an image in a Facebook post?
but for Web Applications the question
How do I insert an image in a Web Applications post?
would have to go to Meta instead.