I have a couple of ideas for TiddlyWiki plugins I'd like to write. However, I've been unable to find any good tutorials or referenoe info for the "TiddlyWiki plugin API" (which doexn't seem to be formally defined).
Does such documentation exist, or do I just need to look at the TiddlyWiki source and some example plugins?
While there is no comprehensive official API documentation, there are several community projects: http://groups.google.com/group/tiddlywikidev/browse_thread/thread/afe860dd7a7fef77
(Part of the issue is that due to its flexibility, the entirety of TiddlyWiki can be considered an API... )
The TiddlyWiki community is extremely friendly and helpful - if you post your questions to the mailing list, you will get competent help.