Wolfram Alpha launched a fun new search tool this week at imageidentify.com.
In short, you upload a photo and it returns back what it thinks it is, plus if it is able to do so, it might be incredibly precise and show you entity data around it.
It is a reverse image search, like many of the other search engines that do this, but it uses Wolfram's data set behind it to power it.
I covered it in more detail at Search Engine Land, here is a picture of it getting it right:
Forum discussion at WebmasterWorld.