Naldz Graphics has a list of Photoshop actions to enhance photos. I use the Lightroom route to process photos, but some actions can be good to have in Photoshop for inspiration or just playing around.
Archived entries for Image Editing
Designm.ag has a good post listing over 20 photoshop actions.
SEAMonster is a freeware image resizing and cropping tool that uses seam carving. Seam Carving is basically a way of keeping important parts of images intact and removing other parts that have little difference in the pixels (e.g., the sea).SEAMonster can be downloaded here.
I haven't used one before, but it reminds me of another Photoshop plugin called Genuine Fractals. This uses an algorithm to resize images with minimum pixelation. It basically uses a best guess algorithm to fill in pixels of the resized image. This is used in contrast to using bicubic resizing, which resizes an image but duplicates it's neighbouring pixels attributes.