Image help please

I have an image site basically, and i need them to be small thumbnail previews, but the problem is, most of the images are squished and i was wondering if there is a way to have this NOT happen, i mean i know there is just no idea how to center instead of resize for thumbnails. Examples are http://www.nerdlogos.com/gallery

Any help is appreciated.

The page has full-weight images, all of them sized to 150x150 no matter what their original dimensions. If you take a 360x140 image and put it into a 150x150 area, it's going to look "squished".
For the images to look OK you have to maintain their proportions.
In other words, if the maximum area you want them to have is no more than 150x150, you have to have the 360x140 image in a 150x58 area.
Ideally, you should have real thumbnails. Thumbnails that are neither full-sized or full-weight will reduce the page's download time. Depending on your resources, you can do this with your image app and upload the thumbnails to the server, having them in the page linking to the full images. Or if you have server-side image capabilities (like PHP) you can create thumbnails dynamically from the full images.