OpenSimulator IRC channels are on freenode.net. Cuurent channels are
Please be aware that the IRC channels are not manned 24/7, so there can be periods when a question will not elicit a response. In this case, we recommend you either ask the question at another time (lots of OpenSimulator community members are based in the US or Europe) or try the Mailing Lists instead.
As well as using dedicated IRC clients, you can also link to these channels via a browser-based "Webchat" facility