LWille

The php5-gd library on some Debian hosts doesn’t include imagerotate() due to memory leaks.
If you notice that rotating images does not work in the image editor, just install this plugin to supply an alternative imagerotate() function.

ImageRotate

Alternative implementation of GD's imagerotate() function.

Rickard Westerlind

Orangelab

Dramatically improve the quality of re-sized images by making WordPress use ImageMagick instead of standard GD image library.
Features
<ul>
<li>Preserve embedded color profile in re-sized image</li>
<li>Automatically recognize custom image sizes</li>
<li>Allow regeneration of existing images (optionally for selected image sizes only)</li>
<li>Configure image quality or use dynamically computed default value</li>
<li>Optimize different image sizes for either quality or size</li>
</ul>
Lnguages: English, French, German, Swedish, Turkish
Requires either ImageMagick binary or Imagick PHP module.
<h3>Contribute</h3>
Code repo available on https://github.com/orangelabweb/imagemagick-engine/

ImageMagick Engine

Maybe even better.  It uses ImageMagick Engine that is installed and allows me to easily regenerate all my images.

Works as advertised

The thumbnail regeneration could be a bit faster though. I have used it for longer than I can remember, at least 5 years.

Simple, functional

Improve the quality of re-sized images by replacing standard GD library with ImageMagick.

ImageRotate vs ImageMagick Engine