A Google a Day posts a question each day that you must use Google's search techniques to find the answer to. The cool thing is that it freezes the search results from the day the question was posted, so you can't search for the answer directly.
Amazon Filler Item Finder searches Amazon for items of a minimum cost, and that qualify for free shipping, to help you top off the free shipping minimum.
Google Labs' Browser Size takes any webpage and overlays a chart showing what percentage of web users can see which parts of a webpage, based on their screen size.
