is a software that allows you to host a Git server with a Web interface. With it you can manage different linked projects/ressources.
Installing Gitblit is quite easy, download, extract, launch. This way, the service is installed and your team can work on it.
You just have to configure a few accounts (or link the application to an Active Directory) and it's done.
For those who since the begining are asking themselves "what the **** is a Git server?" : to make short, it's a system allowing you to version your source code and do some parallel tasks on the same project without errors.
Some public websites allow you to do that kind of work (if you trust the host), for example GitHub.com or BitBucket.org.
The interest of GitBlit here is to host yourself the same kind of server if the security of projects is a fundamental composant.