TinEye

Logos are great, and so are popular posters or ads - anything that is very well-known.

It is best at finding manipulations of very common images or photo - ones that are similar to the original, but that have been changed in some way.

You provide a photo, by upload or URL, and it finds images that are similar.

TinEye is a reverse image search.

TinEye works great for finding spoofs of images, different sizes of images, and just edited images. It usually has several pages-worth of findings, and the beginning ones are usually resized images; the later ones are the edits and spoofs.

The only problem is that it doesn't work very well yet. I tried about six images before I got one that it was able to find. It is apparently either very finicky and precise, or its database is currently just too small.

If it worked well enough, this would be a fantastic resource for finding all kinds of images. I hope they continue adding to their database so that less popular images can be found. But as it is, TinEye is still a good resource for finding spoofs of very popular images. It's good for at least that - but hey, it's only in beta testing.