Scent is a BIG topic with me. My mother tells me that I always put everything to my nose even as a baby.....not to my mouth. It drove her mad that I smelled EVERYTHING!
Today, I make many varieties of scented soap. I also read everything I can get my hands on about scent. I am currently reading Luca Turin. He's on TED talks.
I mix my own scent blends using essential oils mostly, although I do like some of the pre-mixed synthetic scents. Gotta be careful of toxins though with those synthetics, and not to go crazy mixing them together...
I wash my yarn before i stash it, keeping it in a ball, squishing in a towel and drying whole (takes days to dry). If something doesn't smell great, I add an unscented dryer sheet to the box, dipped in my favorite essential oil or blend.