Samyang has released their 7.5mm Fisheye Lens for Olympus or Panasonic Micro Four Thirds cameras. A problem with most small cameras are the crop factor, limiting you from getting the widest possible shot, but this new fisheye will help you get there for a few hundred dollars cheaper than the Panasonic 8mm f/3.5. What no love for Sony NEX? Don't worry, it appears you might be able to adapt this to something like the Sony NEX-5n with this adapter: M4/3 Lens to Sony NEX
As usual from Samyang, no auto focus but aperture has a dedicated ring down to F/3.5. Since Olympus like to rock silver, and Panasonic camera in black, they are available in two different color schemes. Not yet available on Amazon, but early adopters will find it on eBay (click here).
Samyang 7.5mm Fisheye Lens Olympus / Panasonic MFT