Best places to get DVDs cheap is movie stores (not blockbuster..they sell them at normal prices). I can go down to Family Video and pick up new releases for $10.
White Castle
Van Wilder
Back to the Future (only $20 for all three, at walmart)
MIB
Anything by M. Knight Shyamalan (or whatever his name is) Unbreakable, Sixth Sense, the village, ect
Anything with Will Ferral
And more more more!!