From email to project management tools.
Two open source options are Rocket Chat and IRC.
alternatives to Slack (in the resources section of this talk).
Set yourself up for success with your team by setting expectations early on.
What things will you discuss over chat and what things should you discuss in person or in a meeting?
What needs immediate attention?
What are small tasks I can take care of quickly?
What tasks do I need to work on later and what folder can they go into?
Tools: See our list of 14 open source alternatives for email
(again, it's http://productive.win)