I use Slack for many things and it's great to see how many integrations are available out of the box. But building integrations yourself is extremely easy using Incoming Web Hooks. Wouldn't it be nice if you could see a message in Slack each time a user connects to one of your machines over SSH? Yes it would!

http://sandrinodimattia.net/posting-successful-ssh-logins-to-slack/

(I found this via cron.weekly. If you haven't subscribed yet, you're missing out)