Great idea for a discussion, Peggy. I was thinking along the same lines but hadn't gotten there yet!
So far, I've only blended for fiber content. Well, a little bit for color. My favorite is to dye a white wool with onion skins, breed depends on end use of yarn, and then blend it with 1/3 it's weight in white mohair. It really softens the color of the wool and adds a little fuzz to the finished yarn. For years I've been wanting Deb Menz's book Color in Spinning. I finally bought it!! The KP order went in on Sat. I'm looking forward to lots of fun using her theories, and being able to go beyond this 'safe' combination.
As to fibers I've blended, wool/mohair is about all I've done. I have access to lots of alpaca, now, so I'm going to explore that with wool, and a wool/mohair/alpaca combo. And I have some angora, about 25 grams, that I will stretch by blending with wool, maybe Shetland.
Yes, I do that even when I'm blending for fiber combos. You have to put the batt through several times anyway to have it in good condition for spinning, so you wind up with a more homogenous blend if you fluff the fibers by carding individuals before actually blending. And it is less work in the long run.
Are you reading the intentional spinner? I took her advice an spun y angora and then plied it with the KP marino and nylon and I really love it. Next I am going to learn how to frost with angora. She has a new dvd out I would love to get it is al about spinning exotic fibers.
I went out to Linda's yesterday so DH could load up on alpaca "beans" and to get some fiber to blend with the hair the groomer removed from Rocky and Sunny on Monday. I was planning to add some Merino, but I may just spin the alpaca and canine together (huacaya and poodle, specifically). i haven't made up my mind. The Merino would need to be dyed first, because I want a more uniform color. Suggestions? I'll have photos to post later.
Both alpaca and dog are very warm fibers, higher thermal value than wool. You may want to consider that, and what you plan to make with the finished yarn. Of course, where you live, something made from a blend like that could still see at least three sesons of wear! =)