Using the output of other Visual Studio 2010 projects

This is a powerfull new little feature in the SharePoint Development tools for Visual Studio 2010. In A project, you can use outputs from other projects in the current project.
Before, you had to create these weird post building events to copy the built dlls to the correct folder. Now you can do it easily via the GUI.

First double click on the package and then go to 'Advanced'. You can then 'Add' a existing assembly or an output from an other project.

Select the project and add safe controls for the correct namespaces and references to the class names.