Rogue's visibility can be toggled on and off by pressing the F12 key, and it has customizable transparency settings. It doesn't work with all games, but World of Warcraft and Age of Conan are the two MMOs that have been tested by the folks at GotGame and confirmed to be Rogue-friendly. No word on, say, Warhammer Online or The Lord of the Rings Online (EVE Online already has a built-in browser, so no need there), but feel free to try and let us know how it goes.
Note that for the moment, Rogue only runs in Windows. Mac users are out of luck, though to be honest, we're a bit surprised that neither Vista nor Leopard supports this kind of thing natively. Maybe next time, eh?
[Via WoW Insider]