Google drops Chrome Canary build down the Chrome mineshaft
Yes, Google is offering a Vista-esque four flavors of Chrome now -- with the release of Canary, a pseudo-dev channel build which installs to a different directory (%localappdata%\Google\Chrome SxS\ on Windows). Canary isn't linked to your Google Chrome installs at all, meaning you can also run different sync profiles, themes, and browser preferences.
Apart from the folder change, Googler Huan Ren states that Canary may also receive updates which the dev channel does not. Canary will be the most bleeding-edge official version of Chrome and somewhat of a mix between Chrome dev and the Chromium snapshot builds.
Canary's arrival has a lot to do with the new Chrome release cycle. With stable builds due out every six weeks, beta branching will occur more frequently and "risky" changes from the trunk can now be pushed to Canary prior to landing them on the Dev channel.
This also says a lot about Chrome's early adopters -- there's obviously a crapload of them if Google feels it can support two official, pre-beta builds. Download Google Chrome Canary here and run it in tandem with your current stable, beta, or dev build.
Wait a sec... "Why Canary?", you ask? I'm guessing this is a reference to the old practice of taking a canary down into a mine... If the canary died, it was unsafe and the miners knew to bail out. If a change kills Chrome Canary, they'll block it from the dev build.