Communication:
- chat during the day (hipchat)
- skype for voice calls, usually to quickly discuss something
- Google hangout (highest bandwidth communication, I run my daily standups on google hangout and sporadically for "crisis" moments or "clarification" moments)
Project management:
- trello
Product management:
- prodpad
So the trick is to have a daily scrum meetup on google hangout every morning so that you can explain tasks, check how far everybody got the previous day and update the trello board to reflect the new state. It's the only moment in the day that communication is cheap and high bandwidth.
Knowledge center: Google docs and github wiki
There are other auxiliaries like github, airbrake, circleCI and papertrail that report into hipchat so you can get a sense of the work being done.