OK I would say the softest I’ve used so far has to be the one OTN right now - Lana Grossa Soffice - its a Merino / Cashmere mix with a hint of acrylic thrown in to give it a bit of wear and tearability.
This stuff is SOO soft. The scarf I’m knitting with it is turning out well so far (The Inner Truth Scarf from Magknits), and I just love how the colour looks like it has been dip dyed. I hope the recipient likes this scarf, its for someone who deserves a very big thank you =D
I have also just received my Cashmere / Silk 8 ply from Posh Yarns. The colour quoted is called lilac but it looks more bluey to me. I love the colour and the feel of it so much, I’m going to make Silver’s Palindrome scarf from it. It feels very soft and cuddly!
I’ve heard that Mmmmmmalabrigo is the softest yarn ever but I’ve never had the pleasure of touching it myself!