I don't know if this is what you are talking about, but I know that you can use the "Lens Correction" filter under the Distort option in the Filter menu (Photoshop CS3). Use the "remove distortion" slider to remove or add bulge from the photo.
The best I know is Rectfish. It does'nt crop the image a lot, instead it creates interpolation to fill the "straighten". Using Photoshop's Lens Correction, we will lose desirable amount of image due to crop.