iMore has posted a great roundup of the best free games for the iPad. They list their three top picks in each of 11 categories of games: strategy, shooter, sports, casual, physics, action, role-playing, racing, board, word, and simulation. While all of the dozens of games listed are completely free, they're almost all "freemium" titles, meaning that they offer in-app purchases for additional features. The article includes a trailer for most of the games so that you can quickly get a sense for gameplay.