I wrote a little documentation which gives an overview of the Origami
framework methods.
It is not as complete as the rdoc HTML documentation (or the
sources :), but if you're new to Origami this little cheat sheet might
help you.
You can get it in the Downloads section of the Origami page on Google
code.
http://code.google.com/p/origami-pdf/downloads/list
Cheers,
Guillaume