It's an imperfect world, and we all take imperfect photos. PhotoPerfect Express is a free and simple program to clean up your less-than-perfect photos.
Don't look for many bells and whistles in PhotoPerfect Express, because you won't find any. Choose a photo, then select the method of image optimisation you want from the right-side of the screen, and save the resulting cleaned-up photo.
In two of the methods, a watermark appears; if you want to use those methods without a watermark, you have to buy the for-pay version of PhotoPerfect Express. If you want additional editing features, you'll have to pay as well.