I don't see why SharePoint Stack Exchange wouldn't be your first and best choice... I mean, that's what it is! System-specific Q&A. It's not like you need to stand out from all those other SharePoint Stack Exchange sites... You are the one.
In a comment, Anders notes the desire to link the site to Stack Overflow - well, the "stack" part of Stack Exchange is intended to do just that! It's a bit weird to stop and think about how many SE 1.0 sites chose an "Overflow" suffix for their names, given that the important part of the SO double entendre, the bit these sites are set up to help, is the mental stack...
Anyway, this site has been SP.SE for the entire beta, and now that the design work is underway the branding is gonna continue to focus on SharePoint and Stack Exchange. If you'd like to see a tongue-in-cheek nautical theme, suggest it here... ;-)