Windows only: If you keep a copy of Chrome's bleeding-edge Canary build on hand, you can check out Chrome's optional Side Tabs feature right now. Update Canary, activate a "Labs" feature, and you're a right-click away from vertical tabs.
Open up Canary, click the wrench icon for settings, then click "About Google Chrome" or, if you haven't opened Canary in a while, the "Update Google Chrome" option. After your update, browse to about:labs in your address bar and activate the only lab you see there: side tabs. After that, open any tab in Canary and right-click on it, and you'll get an option to "Use side tabs".
The look of the side tabs panel is very basic, but the vertical space and easier read for those with lots-o'-tabs open might be worth the switch.
Tab tweaks land in Chrome Canary [The Download Blog]