Since Google Chrome's release, everyone has been crying out for screen real estate.
Prism[1] from Mozilla is their answer to the screen real estate problem. It allows the user to encapsulate any web application (or indeed any website) they please in a chromeless window running on its own instance. This allows the user to avoid a browser crash shutting down their online app, and allows them to make use of almost their entire monitor for a single webpage/app. It can be run with Firefox or
XULRunner.
More Browser Real Estate - Try Prism Ehtyar.