My current project is Windjammer Socks from Clara Parkes', The Knitters Book of Wool.
The yarn here from Painted Fleece (sadly discontinued), is great to work with. The main component of this sock blend is Bluefaced Leicester, a wool I've used before on socks with great success. So, I've known for a while that I like it. Now, thanks to Clara's book, I know why I like it.
Bluefaced Leicester Wool is the softest of the Longwool breed category. From the book, I've learned that this sheep produces fiber with "open but smaller curls, a fine fiber diameter and a silky demiluster". It also has a nice long staple length - 3 to 6 inches in comparison with Merino's 2 to 4 inch average. This means it produces a fabric that is durable and attractive. It's slightly rougher than the Finewool Merino, but not uncomfortably so. In my experience, softest is not always best. Socks knit with Leicester wool hold their shape beautifully, last longer and don't pill. A wonderful fiber.