Blockbuster is a good place, especially when you hit them at the right time -- times when they put $3 off their pre-viewed selection. I got Sleepy Hollow for $7. Generally can get pre-viewed for $10-$15. Their prices for new discs isn't too special, though.
I personally haven't seen much in the way of used DVD in B&M stores besides the rental chains, but then again, I don't spend much time in B&M stores.
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My DVD List