Mi madre always seems to sniff out the really good stuff there - she's picked up nice tents, awnings, camping gear, etc from Goodwill.
I like to hunt them every few weeks myself - my current tackle bag for steelies/salmon came from Goodwill for $5. I'm always on the hunt for the nice old-school fiberglass rods. I almost bought one the other day, but it would've taken a LOT of work to get back into shape - it had a broken tip section, and even w/ the missing tip, it was about 9'6" - medium heavy casting rod. The cork and the aluminum reel seat were good - but the guides were all shot (not a big deal, it'd get all new aluminum oxide guides anyway) - but the blank looked like it had been exposed to heat - it had two or three waves in it.
Goodwill has been a godsend in other areas though - my wife & I are expecting a little one very, very soon. We've bought 95% of the baby clothes from goodwill - most have been new with tags on them for pennies on the dollar, other stuff is really gently used. Goodwill is good stuff!