When I'm ready to buy, I'm going to look into www.dealextreme.com. They have connections to Chinese or Hong Kong factories and seem to source from factory over production. They ship directly from Hong Kong and their supply lines are not as reliable as what we're accustomed to but if you're willing to wait from 1-4 weeks, they often offer unbeatable prices.

I'm not a flash light enthusiast, so I can't offer great advice on any particular model, but they have quite a selection. http://www.dealextreme.com/products.dx/category.999

I would look into the Cree, Fenix, UltraFire, SSC, etc brands at around the $20 price range. These are some I have considered:
http://www.dealextreme.com/details.dx/sku.36357
http://www.dealextreme.com/details.dx/sku.39765
http://www.dealextreme.com/details.dx/sku.39359
http://www.dealextreme.com/details.dx/sku.16501

What makes some of these lights a bargain is that the bodies aren't necessarily designed to handle the heat generated by the LED for long periods of time and may require some modification to improve the heatsinking of the bulb for extended use.