The liberation-tech list is interesting sometimes: https://mailman.stanford.edu/mailman/listinfo/liberationtech

The rest of the mailing lists/IRC channels I read are all related to specific software projects, though.

I feel like I should add something here about how spending a lot of time on IRC can be inversely correlated with being someone who's doing a lot of work, in some cases. The veterans you're seeing might be people who now spend more time talking about technology than creating it, unless they're using IRC to coordinate their contributions to a project with its other members.