Five years ago...
"Where did you get that shirt?" my friend Jake asked.
"Goodwill."
"Oh." Looking confused. "That's a good place to shop."
"Sun's out, guns out."
I don't buy clothes there anymore (makes me feel itchy), but I love looking through the books. They always have a large selection. However, most of the books suck. I keep going back though. That's because I found one of the best books I've ever read there (Witch Child by Celia Rees).
You will also find tons of DVDs and CDs for cheap (if you're into that kind of thing). If you're not into that kind of thing, you can always drop stuff off here and get a blank receipt, then write-off three dishwashers, two microwaves, and a pillow (disclosure: I'm not qualified to make any tax-related recommendations).
Some people will knock Goodwill, but it's really like a one-stop garage sale, which makes it like a treasure-hunt experience.