Metaprogramming resources and metaprogramming formalisms

Hi, I am putting together resources for metaprogramming in ruby and I am
looking for material.

When I have enough material I intend to put it together both as a
booklet
(The Way of Meta) and a metaprogramming resource page.

Can you guys help me with some good references besides the recent very
good
artima article?

I am particularly interested in ways to ‘formalize’ and organize
metaprogramming tricks in more reusable design solutions (contracts and
aop
come to my mind)

thanks!