Apparently Google just can’t get community testing and feedback for Chrome fast enough, so it has decided to roll out yet another way to access experimental builds of Chrome, called the Canary Build.
The Canary Build will basically be a build that Google will release usually without any human testing whatsoever, and will come out more frequently than builds on the Dev channel, which is currently the most frequently updated testing version of Chrome. In addition to the Dev channel, there are also Beta and Stable versions of Chrome.
This build will be extremely unstable according to the Chromium blog and will only be available at first for Windows users (though Windows users will be able to flag issues for the Mac/Linux teams to look at). Also, Google says that Canary cannot be set as the default browser, so basically, Canary releases are not intended to act as a usable browser almost at all, but only for bleeding edge folks that are looking to help Chrome in the race to be better and faster through a faster feedback loop.