One of my knit night friends was just telling us about the braided join! I hadn't heard of it, but just now looked it up. I have a cotton blend sweater I'm anxious to try this on!
Here's one for two color join. She used a different ply, finer weight yarn for the second color just to show it could be done with different plies, but I wouldn't knit like that because a sudden change in weight could affect your gauge.
She says don't cut the ends till you're done and it's washed which I think is a good idea.