Options to allow users to chat with providers on a site

We have a website, and want to allow users on the site to chat with the providers (if they are online). To make it as simple as possible, we'd either ask the providers for their Google Voice/AIM username or just ask them to have our website open.

Any ideas on best ways to implement this (we are using HTML5/CSS3/RoR3 and don't support old browsers) or even better, perhaps a solution out there that does this. To my knowledge, olark, livechat, etc don't provide this...

FYI: I prefer an open 开发者_如何学Csource solution vs. building it myself.

There was a recent railscast regarding messaging where Ryan built a chat program with push support (not polling). Seems a decent place to start if your requirements are easy going:

http://railscasts.com/episodes/260-messaging-with-faye