Tons of stuff. DH and I tend to go thrift-storing for our dates.
On our most recent trip, we found this physics kit for $2.99, this coverall for DS for $2.50 (we'd planned to buy something similar for him next winter), an antique meat grinder for $10 that we should be able to sell for $75, and a set of phonics books for $3.00.
They had a $5/basket sale at one recently, and we got pretty much an entire wardrobe for the toddler (plus a few shirts for me) for $5 - you can fit an awful lot of todder clothing in a basket if you fold it carefully :)
The kids have a huge library because kids books are $0.10-$0.25 each. Even limiting myself to no more than $1.00 a trip, we end up with more than we have shelf space for.
One store regularly has natural parenting stuff at prices way lower than typical used online prices - fitted cloth diapers for $2.50 and things like that. I got a EUC Hotsling for $4.00. Unfortunately, not my size, but I love the color and pattern. I think I'm saving it for a present (I suspect it would fit my sister-in-law if they decide to have kids soon).
DH just picked up a computer at an estate sale for $10. Not the most recent model, but perfectly functional for what the kids need (flash games and so forth).
We got something like 16 wool blankets for $1.00 each a few years ago. VERY basic - grey and scratchy - but they're servicable as an extra layer, and I've been making nicer blankets by sandwiching them between two pieces of flannel.
I do find the clothing sections overwhelming. While a large percentage of our clothing is from thrift stores, I really only look at the clothing when I know specifically what I need.