BaseCamp + Slack has been a general win for us.

We use BaseCamp for anything that should have any temporal meaning beyond the present, and Slack for water-cooler conversation, coordinating tests, coordinating releases, hot-topic issues, and similar. Basically, anything that is best served with a post-mortem or no record at all goes in Slack.

Slack can be totally ignored and one can remain a positively contributing member of the team; but it exists because we're social mammals and we _don't have an office_. Slack _shouldn't_ be ignored because it is a place of coordination and rapid response, but it _can_ be if one wants to focus on a particular task.

That said, Slack's VoIP for meetings sucks when you have more than a half-dozen people.