Tineye and Firefox... Honey I'm home! Rated 5 out of 5 stars
What a versatile tool!
I've used this to check for any unauthorized use of my photography on the web, to look up more information on images that are not really explained on random sites, and to find stock graphic design for web development.
I love Firefox for the seamless add on integration, and in fact for my personal web surfing it's the only browser I'll use.
I have tried the others during bug testing for my websites and nothing is as powerful or versatile as Mozilla Firefox with add ons like this!