If you're just starting out, try the free ones mentioned in the second post. jEdit is available on Mac as well as Windows.
TextMate and Coda are very popular, especially among web developers. Coda's got some features to publish your files from your local machine up to your production website.
Vim and Emacs are text editors, more plain text than GUI.
Eclipse, Aptana, and NetBeans are IDEs, which are editing tools specifically for programmers. If you already use an IDE, you don't need recommendations for editors.