Chromium - it is like nightly builds of Firefox, sort of, but for Google Chrome

If you think your Chrome install updated over the weekend, it most likely did. The original version released was build 1583, and the build out now is 1798.

I'm sure buried in the EULA somewhere is that it can update behind your back without any notification too.

If you want to be riding the bleeding edge, download the newer snapshots from here.

As of a few hours ago, the Chromium build number is up to 0.2.152.0, whereas the current installed version of Chrome on my system seems to be version 0.2.149.29.

Much like the Firefox trunk builds, Chromium installs into a different directory than Chrome, so you can run them side by side if you wish.