This has been out for a while, and I remember glancing at it last fall, but I didn't fully appreciate it then. TiddlyWiki is yet another wiki implementation, but with a difference: the entire wiki, including the implementation and all the data, is stored in a single HTML file. The file is displayed in a browser, where the content can be read and edited. A "save changes" button writes the HTML file back to disk.
First: this is very clever as an architectural design. There's no server to worry about, and anyone who can open an HTML file (who can't?) can read the content. It even allows for unique deployment scenarios like WikiOnAStick (put the HTML file on a thumb drive, and carry it with you anywhere).
Second: holy cow, the mad technical skillz displayed in the implementation are awesome!