[1maginary]

It's been mostly reduced to free software projects channels/networks and just semi-private channels for groups of friends who've been on IRC for years now. So #archlinux, #dolphin-emu, #python, ##machinelearning, etc. all on Freenode are pretty active.

There's some hobby and subreddit related channels too. Like ##chess, and #rubik.

Other than that, the language learning community was surprisingly very active years ago, so it's still kinda alive. Language-specific channels like ##deutsch, ##espanol, etc. on Freenode are kinda alive. There's also ##learnanylanguage.

[gwd]

I use #xendevel to collaborate with other Xen developers basically every day. Also use #centos-devel, #centos-virt, and #centos-meeting for various CentOS-related things. Also lurk on #golang-nuts and occasionally either ask or answer a question on there.

But it's all more or less work-related now.

[jolmg]

I was once surprised to find that there is also active porn IRC servers. It's unexpectedly mainstream.