Chrome had side tabs for a long time. It was a 'hidden feature' you had to enable in the about:config screen. But Google knows how you're supposed to surf, and vertical side tabs are not it. So they tore it out. Many issues were opened on their bug tracker asking for it to be replaced, but the final word came down - 'we don't like vertical tabs, and therefore no one can have them. Stop opening new issues.'
Sheez. Why not enable users to drag any tab to anywhere along any edge of any window?
Tabbed window manager with pie menus for The NeWS Toolkit 2.0, from 1991: http://www.donhopkins.com/home/movies/TabWindowDemo.mov
NeWS PostScript source code: http://donhopkins.com/home/archive/NeWS/tab-3.0.2.ps.txt
Also, you should be able to push and throw windows around on the screen, and they should bounce off the the screen edges! ;)
Here it is in Lisp for Genera: http://www.donhopkins.com/drupal/node/103
And in Forth for X10: http://www.donhopkins.com/home/archive/piemenu/uwm1/hacks.f