I occasionally use Hugin for de-fishing:
Hugin - Panorama photo stitcher
It's actually a stand-alone pano stitcher but it de-fishes just fine and lets you correct perspective distortion at the same time (if you're going to bother making all those lines straight you'll often find yourself wanting to make them parallel).
It's quite powerful but perhaps hard to use:
- load the image
- select "fisheye" lens type
- go to the stitcher tab, select rectilinear projection
- click calculate FOV, click calculate optimal size
- output as remapped images
- look at the preview
- maybe play with pitch and roll to correct perspective distortion, repeat FOV/size
- click "stitch now".
BTW, at 17mm you should be able to straighten
all the bent lines (a rectilinear projection), but at 10mm this is essentially impossible (the corners get infinitely stretched out). You can do a cylindrical projection on a 10mm image, straightening the vertical lines only.
You might also want to try the Fisheye-Hemi plugin:
Image Trends - Digital Imaging Products - Fisheye-Hemi Plug-in - Specifications
Fisheye-hemi isn't very flexible (only three settings, essentially 8mm, 10mm, and 17mm-ish) but others really like it.