+1 on the Exchange here at BF. I've met some great guys buying here. There are other knife forum websites, but I like the community here at BF. There's one particular site that seems to specialize in balisong flippers; not my thing, but if you like balisongs go check the site out.
I've had nothing but good experiences buying from members here at BF.
Pawn shops and flea markets are a mixed bag. Pawn shops google eBay prices on all their incoming stuff so don't expect screaming deals.
Garage sales can yield finds, if that's how you enjoy spending Saturday mornings.
Lots of great deals on eBay; research prices first, set a spending limit, stay calm and don't get swept up in last second overbidding to "win" over some anonymous sniper. If you miss one there will be another along soon.