Google made 64-bit builds of Chrome available in the Dev and Canary channels during the early part of June, but as of this week, those 64-bit builds have graduated to the Beta channel. So if you were waiting for a more stable version to try, then now is the time to grab a copy of the new 64-bit build for your system!
One thing to keep in mind is that if you are currently running a 32-bit version of the beta channel, then this will overwrite it, but will preserve all of your settings and bookmarks.
Note: The download page will detect 64-bit systems and provide the appropriate installation file.
Download the Google Chrome Beta Channel 64-Bit Release [Google] Note: Only available for Windows 7 and 8.
Announcing the Chrome 64-bit Beta Channel for Windows! [Chrome Releases Blog]