I have added my first actual deployment contributor to my deployment contributor project:
https://github.com/DacFxDeploymentContributors/Contributors
The idea is basically for people to share ideas about writing deployment contributors for SSDT and help each other. If you don't know what a deployment contributor is then you are missing a real treat. A deployment contributor lets you modify the t-sql that SSDT creates to upgrade a database from one version to the next.