The developers behind MacJournal admit that you can use a traditional word processor or text editor for journaling--but they say that's like Lance Armstrong using a bike from Wal-Mart to race in the Tour de France. Aside from the fact that Armstrong would probably still kick butt on a Wal-Mart bike, they've got a point: MacJournal is one of the best journaling programs available for the Mac, with a huge range of features that are useful whether you're keeping a journal for yourself, taking notes for classes or meetings, organizing random snippets of info, or prepping blog posts offline.
MacJournal gives you a fairly intuitive, feel-good interface (especially its green-text-on-black, full-screen writing mode), and a ton of tools for organizing your thoughts and words, including a built-in calendar, good search function, a system of nested entries and journals, and keyword tags, labels, priorities, and other opportunities for annotation. You can include nearly any sort of content, from movies to PDFs to podcasts, and bloggers will like that its formatting translates well to HTML, with support for TypePad, Blogger, LiveJournal, and more. You also get password protection and encryption, integration with Apple's Mail, and a wide variety of export options, such as PDF, HTML, Word, and even iPod Notes.
The only major issue we can fault MacJournal for is the 15-day trial period, which is a little short for this sort of application, especially given its rich and complex feature set. This most recent version adds minor interface enhancements and assorted bug fixes.