chessGMPlay chess against bots from beginner to grandmaster strength. Each bot has its own style, its own favourite openings and its own think time, so a game against a bot feels like a game against a person of that level. There are also bots modelled on famous players.
Pick a bot, choose your colour and start: no sign-up is needed, and every game can be reviewed move by move afterwards with Game Review. To train a specific skill rather than play, try the courses and puzzles.