I'm sure I am the only one who didn't know this until just now, but if you're a Chrome user, you can grab a tab and drag it off, away from the chrome window, and it will get put into a new chrome window by itself. And, correspondingly, you can drag a tab into another chrome Window and it will get sucked in and become a tabbed page in that window.
There's a bit of trickiness to getting tabs to merge into other windows... I haven't yet figured out all the magic, but it definitely does work.
I can't tell you how many times I have opened a new window and then loaded up a page I had open elsewhere so I could compare things side by side.
I wish I'd known about this a long time ago!
