I've been known to purchase (ok, hoard) wool and wool blend sweaters from my local thrift store to take them apart and reclaim the yarn. Yes, it is time consuming, but the more I do it - the better + faster I am at ripping them out.
I'm in the process of ripping this Express turtleneck cabled beauty out, when it hit me - I should totally make a hat out of that turtleneck part. I even surprise myself sometimes with ingenious ideas. It is a bit tight on my head, but fits my son (who is 4) perfectly. So, I'll ripped it out to the ribbing length that I like, pick up the live stitches to knit on wards to make a really quick hat - no cast on, no ribbing, but hand-knit (well partially).
The yarn is a bit Green (with a capital G) so I may tone it down a bit by throwing it into the dye pot for an experiment. But it is worth rescuing this yarn for it's fiber content - 40% Merino Wool, 30% Viscose, 20% Angora + 10% Cashmere - good stuff!