There are many challenges to keeping a large development team organized, especially because we work on multiple projects at a time. We have seven CMS developers on the Earthling Business Services (websites and ecommerce) team and we use a ticketing system to coral all of our support tasks. Ideally, nothing should happen on a project unless there is a reference ticket for that task - it doesn't always happen that way, but that's our goal.
We use git repositories for tracking code so it is easy for a developer to hand off a project or for a new developer to step in when extra help is needed. Earthling's DevOps Solution Architect created a Docker environment to make it easy for developers to easily set up a local environment and move between projects.
Sometimes the biggest challenge is prioritization, in other words figuring out "who gets worked on next?" But that is one of the great things about having a team of seven skilled developers because we can shift work loads around to accommodate projects at all of their various stages.
If we didn't have a strong system for organizing our workload we wouldn't be able to serve our clients as well as we do, it just wouldn't happen.