Does there exist a channel (or channels) for the Foundry in the in game chat? A place where aspiring Foundry authors (such as myself) can go to ask for advice and tips or those wanting to find a good mission can go and get suggestions on which ones to play or ask for advice about a certain mission if they get stuck?

There's one called "Foundry". I imagine that would work. :p

The trouble with an in-game chat channel is we can't see chat when we're working in the editor, which is the majority of the time. So, most of the Foundry authors probably won't be available to respond. The only responses you'll get are from those not working in the Foundry at the moment and those who happen to be previewing at the time.

I think it would be cool if there was an option for in game chat in the foundry but I have to agree with Duke-of-Rock.

For now the best option for foundry-related discussion is the StarbaseUGC chat http://starbaseugc.com/index.php/chat/

This is useful for help in doing something in the foundry, or just discussions related to plot, maps getting people to play, etc.