Hello,
I have created gitter room for each module and also invited some module leaders.
You can join following chat room if you are volunteering in following modules.
With reference to Foundation Wiki - #25 by kolate_sambhaji we (@revant_one and @strixaluco ) decided gitter.im is good tool to communicate as It is easy to join and ERPNext already using it.
For group call conference call you can use Jitsi Meet anytime. Its similar to go-to-meeting and it is open source.
gitter room:
ERPNext Marketing
ERPNext Account
ERPNext CRM
Healthcare
Manufacturing
POS
ERPNext Projects
Note:
I am still adding all module and inviting users to group.
If any module is not present, then please let me know with your github/twitter id, so I will create it.