jmh suggests the use "anyone" and i'd like to add "everyone" as in "what's everyone doing tonight?"
this comes back in a way to emanuela's italian point about "lei" the "she" for the formal "you". "voi", the plural "you" was also acceptable until some time in the past, i believe, but was changed after the second world war. (please correct me if i'm wrong, emanuela!) "lei" is a superbly indirect way of addressing the speaker and seems to have some parallels in highly formal english as in "your honour" or "what would her majesty like for tea?" which assumes a third person present since addressing the individual directly would be brash.
in this way "would anyone like to go out for a beer?" is an indirect way of addressing the people present through an anonymous group which is understood by everyone present to be the actual group. am i reading too much into it?
one other point. thou seems to me to be used today only with a deliberately clumsy attempt to match an old fashioned verb to it, usually in creating an 11th commandment: "thou shalt not take mine beer from the fridge unless thoust payest first". not a bad commandment when you think about it...
