I've gone through a number of the Chrome extensions and most of them add nice functionality or easy access to services like Google translate. Alum by Brett Slatkin , an infrastructure engineer on the Google App Engine team and co-author of pubsubhubbub, has written the first extension that actually adds to my productivity.
In brief, it allows you to open multiple copies of Chrome in a tiled configuration that you specify in the options panel. If, like me, you frequently have multiple browsers open, each with a associated topic like, webservers, tech docs, admin consoles, news, email, etc. this has been a balm. It allows you to rotate the browsers left or right, and to bring the browser of current interest into focus. I generally keep one larger window open on the left with the other windows stacked to the right.
There are one or two limitations that may be intrinsic to Chrome at this point. If your focus is in a New Tab or an open Google Doc, the rotate keys will not respond. Also, if you attempt to override system level hot-key combinations you will not succeed.
In Ubuntu, I use:
Open windows - Shift + Control + Meta + O
Rotate right - Shift + →
Rotate left - Shift + ←
Move tab to window - Shift + Alt + Number
It is interesting that it was not written by a UI specialist, but by an engineer to solve a problem close to home. I think that some of our best software engineering ideas are born out of irritation. Now, if someone could just become sufficiently irritated with threads.
Instead of trying to imagine it, checkout it out at: https://chrome.google.com/extensions/