RedNotebook is a simple diary or notebook application written in Python. It uses a subset of the txt2tags markup for formatting: Headings (but only one kind === Heading ===), bullet lists, bold, italics, underlining, and strike through. The cloud feature looks cool, but in the end the program is rudimentary. If you need a simple electronic journal, I would recommend it. It's written in Python. It is available for Unix, the Mac and Windows.
The txt2tags markup is actually very close to the ConnectedText markup, and I am tempted to write a script that converts from CT to text2tags, if only because txt2tags allows you to import to a variety of other formats (including TeX). But I am not sure whether TeX isn't overkill for my purposes.
1. There is another application written in Python that is supposed to be a wiki. It's called Wixi. It is also based on txt2tags, and it implements the entire feature set as far as I can see. But the wiki links are designed rather clumsily—or so it seemed to me. It also hung up on me a few times. It also runs on Unix, Mac, and Windows (and is probably the worst on the latter).
2. There is at least one more problem. Txt2tags does not do footnotes which are much more important to me than tables. Just take a look at this blog :)