SubEthaEdit

SubEthaEdit is a collaborative distributed text editor, combining the simplicity of TextEdit and the power of Rendezvous. It allows to share documents on a local network (with Rendezvous) or on the internet. Every participating user can type simultaneously and see what others are typing. You can even follow others users to see what they are up to.
SubEthaEdit features true simultaneous editing for multiple users. Text changes are highlighted in a different color for each user, allowing easy identification of your coeditors' changes. The scrollbar indicators give you a quick overview where others are working in the document.
In addition to its rich networking capablities, SubEthaEdit does everything you'd expect from an advanced text editor. Encodings and line endings are handled seamlessly. Programmers benefit from customizable syntax coloring and function pop-up, bracket matching, indenting and regular expression find and replace.