1. Manos del Uruguay Alegria : at 425m/100g this is nice thin stuff. It's a 75/25 merino/nylon blend, though, so it's soft. I was seduced by the truly eye-popping neon colours...the colourway I picked (9452A or Candombe) is quite random, so doesn't pool or stripe as much as some of the others appear to (check Ravelry for projects). However, some care is still required if you don't want unexpected blobs of colour to appear. The socks are kind of floppy, as expected from a merino blend. The softness/floppiness gets accentuated with washing, and the stitch definition (both due to the colour and the fiber) isn't the greatest. After several wear/wash cycles, the socks have started to fuzz a bit, and they are getting a bit "grotty" - the colours getting dingy, especially at high abrasion points. My son still loves 'em though. Not sure I'd get this stuff again, myself - at least, for socks. It's too soft for me.
2. Ancient Arts Fibre Crafts 75/25 superwash wool/nylon blend : I got two skeins of this, one dyed in a "cat" colour (Russian Blue to match our cat Misty!) - with part of the proceeds going to Calgary's Meow Foundation for stray/abandoned cats - and one in a deep wine red (Bordeaux). Ancient Arts is an artisan dyer based in (I think) Alberta, and they are frequent visitors to fiber fairs in my area - I picked these skeins up at Vancouver's Knit City. The base is 400m/100g, not merino (so not as soft as that above), and has a tendency to splittiness, which can be annoying while knitting. It produces nice elastic socks and has good stitch definition. The colourways I picked are nicely marbled and don't pool or stripe. I would use this stuff again, although I still prefer Woolen Rabbit Pearl as a "special projects" yarn, and plain old Regia as my go-to workaday sock yarn.
[Russian Blue socks]