Here's the scoop on the blue and white sock yarn:
It's Froelich Wolle Blauband MaxiRingel, in color #7717. Each skein comes with a card of matching reinforcing yarn (I'll find them eventually, I hope.)
I'm pretty sure the yarn came from my not-local-enough LYS Whippletree in Woodstock, Vermont - and out of the sale bin, even. I'm loving this little yarn more and more - the skein is totally squooshy, the colors are favorites, and it's behaving beautifully. No idea why it's taken until the second sock to appreciate it so much.