[transitorykris]

The Lean Coffee hand signals includes a couple others that aren't in this blog post.

http://www.lovelifepractice.com/practice/using-hand-signals-...

Another hand signal I've used in large groups is pointing at a person who has a hand up (wants to say something). It's a useful signal to the person speaking and can avoid people stepping on each other to speak next.

[peteretep]

Ironically I've used exactly this to generally shut down interrupters I didn't want. Point at them when you can see they're about to interrupt and then keep talking. Indefinitely.