<a href="http://mozilla.zeniko.ch/fission.xpi">Fission</a> combines address bar and progress bar -- Safari style, as did Fusion [screenshots]. Should you prefer individual progress bars for all tabs, have a look at Tab Mix Plus instead. Note that some themes might break when you install Fission. If that happens for you, please contact your theme's author and ask him/her to adapt the theme for Fiss