This is a sample gallery for Sigma 10mm and Samsung 10mm diagonal fisheye lenses, suitable for APS-C cameras. There are several programs available for remapping the images into other projections besides the one that they come out from the camera. Two programs that I have tried are PTlens and Fisheye-Hemi.

PTlens program can be used to remap images from a fisheye lens into rectilinear images (but the program can also be used to remove barrel/pichushion distortion from calibrated lenses, CA, vigneting, etc).
PTlens home page: http://epaperpress.com/ptlens

The Fisheye-hemi uses a different remapping method for fisheye images - it preserves more of the original composition and retains more pixels (crops a lot less from the original), preserves perspective of the original image, but achieves to straighten vertical lines. Doesn't work as well for exterior architectural shots, works better when photographing people, etc. Unfortunately, it appears that Fisheye-hemi does not work 100% accurately with Canon APS-C cameras, because a 10mm Fisheye-lens produces a 167 degree FOV on a Canon camera and the program presumes that the lens produces a 180 degree FOV, thus overcorrecting the image and producing distorted lines. You can circumvent this problem by increasing the *long* side of the canvas by about 7% before applying the filter and then cropping afterwards the borders.

UPDATE: I hear that a new 2.0 version of the Fisheye Hemi is coming by the end of the year 2010 and this version will support an APS-C sensor with a 10mm lens.
UPDATE2: The end-of-the-year release doesn't seem so likely as I haven't had any reponse to my query from the company about the v2.0 and the release date.
UPDATE3: It's a shame that the version 2.0 never happened, but at least you can use the method of increasing the canvas size of the long side before applying the filter.

Fisheye-Hemi plugin can be found here: http://www.imagetrendsinc.com/products/prodpage_hemi.asp