Just to add another quick note to this, subethaedit is also accessible.
Admittedly, it's shareware, but it *is* an alternative, if for some reason you're not happy with Smultron.
It's also got an interesting ability to let multiple people edit a document at once.
I'm just annoyed that I can't use Textmate, which is the editor most of the OS X programmers go nuts for.
