There are some in The Complete Metalsmith by Tim McCreight, and he
has another little book called Japanese Patinas that is so cool.
Really different stuff you might not have heard of.
Of course the big book on the topic is the expensive, The
Colouration and Patiniation of Metals. Very cool though, lots of
color pages showing the finished products.
And, to buy pre-made stuff, check out Sculpt Nuveau.