Slack: communication tools
This is just a perfect example of B2B communication tools. Free to 8USD/mo+ is more than enough to setup a standard communication tool in a small company (i.e. startup, or SMB) just to cut the never ending story on xmpp/skype/email/etc.
And as any geek, they got me on “integration” section:
For those who’s got a missing bit of team communication in their shipping/communication chain for product delivery. This one’s for you folks!