Amazon has the Samyang 16mm f/2.0 (another branding of the Rokinon 16mm f/2.0 ED AS UMC CS) for $319.00.
This is a popular value manual-focus wide-angle lens for crop sensors. You can see sample images in the flickr group for this lens.
This lightning deal only runs for 4 hours (until 2 PM ET, or until sold out).