Favored Freeware: SubEthaEdit

SubEthaEdit is a powerful and lean text editor with advanced collaboration features. By combining the ease of Bonjour with the world’s best text collaboration engine, it makes working together not only possible but even fun.

Pros: SubEthaEdit is a solid and stable plain text editor. The Bonjour-enabled collaboration support makes this application an invaluable tool for almost any Mac-based collaborative development team. SubEthaEdit is free for non-commercial use. Commercial licenses are only $35, with price breaks starting at 3 licenses.

Cons: None significant.

Note: SubEthaEdit is no longer available for free. Use Smultron instead.