Preview Featured Image – Crop to size?

I’ve been using this plugin to display sub-pages on an upper level page, using the featured image as the image preview. However, due to recent design tweaks, the featured image (which on posts and sub pages is displayed as a full-width header) had to get shortened in height. Well, this makes the preview images look lame now, way too long and short. I know I could probably show the “first image” instead, but the person I’ll be handing this site off to isn’t savvy enough to really handle that. Using the featured image is best.

That being said, is there a good way anyone knows of that I can crop the preview of the featured image to the dimensions I want? Could it be a matter of generating different sizes and dimensions of the images uploaded to the media library, then somewhere in functions calling out a specific version of the uploaded image? Looking for suggestions, thanks!

http://wordpress.org/extend/plugins/page-list/