real-time updates with WebSockets, what's your strategy

I'm building a new feature that needs to update lots of clients all at once, in real-time. My first idea was WebSockets, but I'm curious about the best ways to handle the connections, deal with folks dropping off smoothly, and send messages out effectively when there are tons of users. Any library or design ideas you'd suggest for something that could end up with thousands of connections at the same time? Also, what should I watch out for when I actually build this?