Sorry, I don't really know any reference sites, however I know that two of most common blends (JBM and Kona) usually use Central American and light South American gourmet coffee crops. I would suggest finding a very light-bodied coffee that won't overpower the taste of the Kona/JBM, and trying your own blend.
I agree with blending for espresso, however why blend anything else if the quality of what you purvey is good...Flaunt It!
Tell them about that super chocolaty, mouth filling Huila or whatever it is.
Hope that doesn't sound too righteous...but blending's cheap cutting in most instances, right?
This may not cover everything you want to know but it is the only info I've seen online on several subjects in cluding blending. It is more principle based than do this do that. Usually I find this more useful. YMMV. You have to poke around a bit but it was a very fruitfull sight for me. Very good info on milk steaming techniques and tamping.
