I have been using IRC for for 14 years now. I began with DALnet, EFnet, Freenode, OFTC, etc. These days, I just use Freenode only because all the main communities around open source technologies seem to hang out there.
Before StackOverflow was founded and became a thing, Freenode IRC was my primary source of help when I encountered issues in open source tools. I have learnt a lot from the #debian, ##math, and #not-math channels, especially.
Some of my favourite channels on Freenode IRC include #lisp, #emacs, and #python. They have great communities with many regulars who have great attitude. These channels are also quite friendly to beginners. I still remember an interesting incident from 2006 when I posted a mathematics question to one of the channels. The channel was mostly quiet. After about 15 minutes, I got detailed answers from multiple members of the channel. 20 minutes or so later, I saw others posting Python questions to the same channel. That is when I realized that I had inadvertently posted a mathematics question in the #python channel. :)
I don’t know if you consider freenode to be “hosted by corporations” but if you don’t, the channels dedicated to both specific libraries and the languages themselves are at least active, last I checked.
The one downside I’d point out is that language channels tend to be filled with purists, of the, “ you shouldn’t want to do that” variety.
Before StackOverflow was founded and became a thing, Freenode IRC was my primary source of help when I encountered issues in open source tools. I have learnt a lot from the #debian, ##math, and #not-math channels, especially.
Some of my favourite channels on Freenode IRC include #lisp, #emacs, and #python. They have great communities with many regulars who have great attitude. These channels are also quite friendly to beginners. I still remember an interesting incident from 2006 when I posted a mathematics question to one of the channels. The channel was mostly quiet. After about 15 minutes, I got detailed answers from multiple members of the channel. 20 minutes or so later, I saw others posting Python questions to the same channel. That is when I realized that I had inadvertently posted a mathematics question in the #python channel. :)