Have you tried Google hangouts? We've been pretty happy with its screen-share (Hangouts with extras).
Also we use redmine as a wiki+issue tracker with git integration. An almost github like setup :)
Also we use redmine as a wiki+issue tracker with git integration. An almost github like setup :)
Hangouts on the other hand is quick to start with, free and chat, screen sharing, scribble pad work seamlessly across all platforms.