Hubot is a framework to build chat bots, modeled after GitHub's Campfire bot of the same name, hubot.
Hubot is shipped with a small group of core scripts: things like posting images, translating languages, and integrating with Google Maps. GitHub also maintains a repository of community Hubot scripts and an organization of community Hubot packages that you can add to your own robot.
The real fun happens when you add your own scripts. Be sure to personalize your Hubot, too; your company's robot should be a place full of inside jokes, custom integrations, and general merriment.
Hubot is extendable with scripts and can work on many different chat services. Here are the most popular ones: