Just used this and it worked like a charm.  I did a screen capture, cropped down to a portion of an image that was on my screen, saved as .jpg, and then uploaded to http://www.tineye.com.  Within seconds, it returned two websites that had the original image (neither was the source of my image) and they were complete images rather than the cropped version I uploaded.  Pretty cool.

So never again will the likes of 'annamama' come on here and fool us...
http://www.tineye.com/search/7532a8dd5b6aa0e54e1ca45818a583fe869db655/

I didn't realize that, but even so, did you take a look at some of the matches it was able to make.  Lots of edited versions but it still found them.  Better be careful stealing images and using them (even edited) on your websites.  The copyright police will find you...