When I have a smalltalk with someone I have not seen for some time, I dread the question "Where are you working", because after I'll say "WorkLight, it's a great startup.", the other guy will ask "What are you doing?" and I just hate that question.
The short, incomplete answer will be something like "we develop server software that help the buyer to reach its users out side of its usual reach or where their users are, on the web (iGoogle,Netvibes, Facebook), on the desktop (Adobe Air, Vista Sidebar) or on their mobile phones (iPhone, blackBerry), by writing easy to develop and deploy, rich and secure application.
I can talk about it for hours, I can give examples from now till tomorrow, but I do not have this 30 sec. pitch to give in this kind of situation.
So what do I do? Roll my eyes and say "you know, a start-up".
