Michael Mallon wrote a review of injinji Outdoor Quarter Crew Toe Sock- NuWool on November 12, 2009
I've tried many a brand of merino wool socks, and the Injinji are hands down my favorite.
They're not the absolute lightest weight, but still fairly light (my size large nuwool outdoor quarter socks weight almost exactly 2oz / pair) while being extremely comfortable.
It may take a few wearings to get used to the idea of "toe socks" but after your first decent hike/trek in them, your feet will thank you, as they prevent rubbing of the toes, and as such really do delay the onset of blisters.
These are the only socks I'm brining on my John Muir Trail hike, and will likely be my go-to sock when I attempt the PCT as well.