When I started using Git around 2006, we didn't have GitHub. We used Google Code for SVN hosting, but we wanted to try Git because it was 'truely' decentralized, so we just pulled from other developers' computers directly. It involved setting up port forwarding on the router and letting your computer on 24/7. Fun times.
We did something similar, but used a dedicated server we already had on the network instead of another dev's machine.