Help Me, Oh Knowledgeable Friends

I'm looking to get a microphone that is compatible with my Mac. I'm thinking of this one, of which I've heard good things, but I don't want to settle for it just because it's inexpensive. Does anyone know anything about the Logitech mic? Or can anyone recommend a different one that's good and, say, $100 or under?

A Yarn-Related Ponderance

(to some extent, I blame cbpotts.)

Does the 20% merino negate the 80% cotton if I'm looking to make lightweight berets for summer?

And does the not-machine-washable negate the whole thing?

With Thanks to mabfan for Reminding Me...

Happy Liza Doolittle Day!