GitLab - Create, review and deploy code together with GitLab open source git repo management software | GitLab
Scrivener - Scrivener is a content-generation tool for composing and structuring documents.
BitBucket - Bitbucket is a free code hosting site for Mercurial and Git. Manage your development with a hosted wiki, issue tracker and source code.
Celtx - Celtx is a scriptwriting software platform with applications in a wide range of mediums but that specializes in helping screenwriters.
GitHub - Originally founded as a project to simplify sharing code, GitHub has grown into an application used by over a million people to store over two million code repositories, making GitHub the largest code host in the world.
Trelby - The free, multiplatform, feature-rich screenwriting program!