The lovely, successful Kickstarter game Sir, You Are Being Hunted is sitting in an alpha state. I'm eagerly awaiting its completion -- it's expected to be in beta within a few months -- so I can be chased around an island for sport by aristocratic robots.
In the meantime, Sir, You Are Being Hunted developer Big Robot has gone ahead and put a free, procedurally generated racer on its website. You can download it for free on Mac or PC. It's pretty cool looking, a bit like the recent Race the Sun.