1. Make sure that you use Google Chrome 9 (beta, dev), Google Chrome 10 (Canary) or a recent Chromium build. For example, you could type about: in the address bar.
2. Type about:flags in the address bar.
3. Click "Enable" next to Tabbed Settings and then click the "Restart" button at the bottom of the page. This will restart the browser.
4. Click the wrench menu and select Options.
5. Select Under the hood and pick a value from the "Page zoom" drop-down.
If you don't like Chrome's tabbed settings interface, you can go back to the standard settings dialog by disabling Tabbed Settings from about:flags. You won't lose the default zoom level, but you'll have to switch to the tabbed interface if you want to change it.
Bonus tip: Another option you can change from the tabbed settings interface is minimum font size (Under the hood > Web Content > Customize fonts > Minimum font size).
{ Thanks, Sterling. }