Peter Borg's "Smultron" -
http://smultron.sourceforge.net/ - is an excellent free text editor.
"...some of its features are tabs, line numbers, support for syntax colouring for many different languages, functions list, support for text encodings, snippets, a toolbar, a status bar, preview, split window, multi-document find and replace with regular expressions, possibility to show invisible characters, authenticated open and saves, command-line utility, full screen editing and running commands and scripts from within the application."
Mac