Seeking a Great Smoothie Cookbook/Resource
Check this out:
Nik used to be here on OH quite a bit. She has GREAT ideas for different smoothies. Last I heard she was even gonna publish a book, but I'm not sure where that project is at right now. There are over 50 smoothie recipes on her website though so that should get you started.
There is also this one:
Michelle (Eggface) is also an OH member. She is pretty active and her site also has many great ideas.
I know there are lots of others but these two are my favorites so the come to mind immediately.
Enjoy experimenting - with all of the information out there it's completely possible to find shake recipes that you actually like and don't just have to tolerate.=)