The best lens you can buy for $20…. a 35mm F/1.7 Suitable for use Micro four thirds & SONY NEX system cameras with an appropriate C-Mount lens mount adapter.
I got mine on DinoDirect.com (though they screwed up other bits of my order, so I can’t really “recommend” them very highly…) where it’s labelled “35mm F1.7 C-mount Camera Film Lens”
It is comparable (and may very likely in fact be the exact same basic lens hardware) as the SLR Magic 35mm f/1.7 MC lens for M4/3 & SONY NEX system cameras
Usually titled “SLR Magic 35mm f/1.7 MC lens for EP1 EP2 EPL1 GF1 G1 G2” or “SLR Magic 35mm f/1.7 MC lens for NEX-3 NEX-5” on their eBay store.
A gallery of test & sample shots taken while I produced the review can be found in my Google+ Galleries;