Bitbucket is a cloud platform where you can save your code and share it with your co-workers. It has a GIT version control, so each one of the coders edit the code in his/her machine and later submit it to the BB server that updates the server version. Bitbucket is similar to GitHub, but it does not require that you make your code open-source as the free-version of GitHub. Bitbucket is free up to 5 users.
You probably know this great tool, but for those who don't know I will explain what it does. Dropbox is a program that you install in your computer and it will make a copy of a folder (that you specify) and its contents in the internet and keep it updated with any modification that you make (e.g., delete a file, rename a file, add a file,...). With a copy of that folder in the internet, you can access it from any place and you can also share it with other people that also have a Dropbox account. In our case, we use Dropbox to share files among all of employees. Dropbox has a free account of 2 gb (up to 18gb, if you referred it to other people).
It provides that same service as Dropbox but we found it to have some bugs regarding updating the files in the cloud, so we use Dropbox to share files among us all. However, Google Drive provides an incredible feature (that is basically the feature of the former Google Docs) that allows different users to edit the same file together, in which you can see what others are doing. This is an incredible tool specially for brainstorming with people in different locations. Google drive free account has a 5 gb limit.
Google Hangout allows you to make video chat with other people, but the main feature that makes it in my list is that it allows you to easily share your screen with others. It is not rare for us to debug a code together using that screen-share functionality. Google Hangout is free, but it only allows you to use screen-share between Google+ users.
Podio is an on-line management tool that not only gives you all basic tools for management (projects, activities, milestones, deadlines, budget control,...) but also has a "social platform" built in it, allowing you to share specific milestones, projects,.. with specific people. You can also include notes and comments in the activities in a twitter-style, so you can easily share with your co-workers useful information about that activity. Podio has a free version to companies up to 5 users.