One of the things I hate the most is writing a synopsis. So, as part of my wiki, I do two things. First, I write a blurb for each major scene or chapter, probably only 2-3 chapters ahead, to function as a loose outline. It usually includes POV character, other characters in the scene, purpose of the scene, and major plot points. Then when I finish each chapter, I go back to my blurb and correct any changes, basically ending up with a brief precis of each chapter.
Then when I'm finished, all I need to do is hook them all together, and voila--the first draft of my synopsis.
This is a close up of the plot tags:
And here's a close up of my precis for chapter 1:
I also jot down any plot ideas I have in their own tiddlers, tagging them as appropriate. Tagging is another amazing strength of the TW concept. Any given tiddler can have any number of tags. So a given tiddler might be tagged 'plot', 'character', and 'theme', for example.
It is also a snap to look at tiddlers in any order you want--very handy if you want to rearrange scenes or chapters.