Bananaslug is a serendipitous search engine. It uses the google API to mix your search term with a random seed and returns results that are probably orthogonal to what you were looking for. Minutes of fun.
Google Compute is a distributed computing project involving users of the google toolbar. It's a light application which uses idle processor cycles to analyse data for "carefully selected charitable projects, with the guiding principle being to help humanity and advance scientific knowledge".