I know a lot of HN folks are very critical of Telegram, but I've been using it for team (and private) communication for quite a while now and it's great.
It has clients for almost all platforms including a nice web client for all browsers.
Same here. We use Telegram for team communication while everyone is out of the office. We've integrated it with github and CI, and now thinking about making this service public: http://telegram.jaconda.im