Google Chrome is the officially sanctioned browser from Google, but the open-source, alpha-level Chromium project has the cool stuff, like basic Greasemonkey support and extension support. Luckily, it's not hard to install and use both browsers on one system.
As the ReadWriteWeb blog explains, the hard part isn't the actual installation, at least on a Windows system. What might be confusing for a newcomer is actually finding pre-built Chromium installers for your system. They're found at build.chromium.org/buildbot/snapshots, along with the "official" Mac and Linux Chrome alpha tests. Grab a copy of the chromium-rel-xp release for Windows, install it, and then enable extensions in Chromium, explained both at the link below and in our look at early extensions.
Chromium's list of usable extensions is growing at am impressive rate, with social, bookmarking, and even IE8-style accelerators showing up in the latest test builds. If you're all about Chrome and want to get ready for the next big developments in that browser, keeping a self-updating copy of Chromium handy is a good way to go about it.