Ask HN: Web app group chat SaaS options?

Does anyone have any recommendations for a free real-time chat widget you can insert into your web application? The idea is to allow site visitors to chat with each other. Something like IRC, preferably. Ideally with an HTML5 interface.

I could just set up an IRC channel and use something like Kiwi IRC (https://kiwiirc.com), or one of the many solutions out there using WebSockets and a separate daemon, but I'd prefer to outsource it to another provider if at all possible. I assume most of the solutions will be paid, but I was wondering if anyone had recommendations for any free ones.

Thanks.