pidgin + libpurple is great, and it makes interacting with Slack and other chat systems I use daily so much better. It's too bad libpurple clients seem to have withered on other platforms (what happened to Adium?)

I really miss the days of a unified chat application (anyone remember how amazon the chat app on the Palm Pre was? It'd seamlessly switch between jabber/aol/messenger and sms)

I've even written my own libpurple plugins for chat systems I've had to use. I do wish libpurple had better tutorials and documentation though!