I have been a fan of
Written? Kitten! for a long time. This simple text typing box rewards you with pictures of kittens for every 100 words you type (or you can set the rewards for different numbers of words):
Now they have a new feature! You can just type whatever you want to be rewarded with in the URL, like this:
http://writtenkitten.net/?search=beach
Written? Chocolate!
Written? Beach!