Firefox: Late last month, a Mozilla contributor showed us how Firefox 4.0 might look. The Strata40 theme and add-on gives your browser that same look, without having to wait or install pre-pre-alpha Firefox builds.
Strata40 and its required side add-on, StrataBuddy, offer many of the same tweaks to Firefox's interface that Firefox 4.0 will likely offer, like moving your tabs to the top of the window or just under the address bar, consolidating the address and page loading bar, and updating the various graphical bits around the browser frame.
The top image shows off the developer's own screenshot of his add-on in action. He's got a nice-looking olive-type Windows theme going on; here's how Strata40 looks installed on a stock Windows 7 copy of Firefox 3.5, with the tabs moved up top:
The developer "requires" about three other add-ons to get Strata40 running "at its best", like Fission, App Tabs and Tab Progress Bar, and suggests that Firefox 3.6 is actually a better fit for his theme than 3.5. Still, with Strata40 installed, Firefox 3.5 can move forward in design time a bit without too much incompatibility risk or, seemingly, add-on drag.
Strata40 and StrataBuddy are free downloads, and StrataBuddy is an experimental add-on. Both work wherever Firefox 3.5 or 3.6 do.
Strata40 [Firefox Add-Ons]