There is one particular use of IRC channels that is insanely useful, that I'd like to share.
On various programming language channels, there are ad-hoc expression evaluation bots that experienced people use to guide newcomers through the intricacies of the language. If you're new to Haskell, for example, what you can do is grab the logs for the past 3 years, grep for "> " (used to invoke the evaluator) and you have instant insight into how an experienced Haskeller's mind works. It can speed up your learning by a factor of 10 compared to reading papers / blogs / formal tutorials. I know because it did this for me.