Just keep at it. My father and brother in law picked up a box with some Nintendo Power magazines, roughly 25 manuals for NES games, a SNes, AV cord, and Controller for 3 bucks. Also snagged a PSONE with flip screen, controller, mem card, and tony hawk 4 for $5.
last weekend I went out and got 3 hint books ($6), 2 cds ($1), and a GBA SP with carry case, 2 wall chargers, a car charger Bratz (yay) and Pokemon Crystal ($5)
Just keep at it. Eventually you find some good stuff.