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).

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.