This is kind of a follow up on my answer there: http;//mozilla.stackexchange.com/questions/20/speedtab-a-quick-way-to-get-to-a-page/35#35
Actually, answering this post got me thinking... so here I go:
Tab Dock would act just like a dock, combining bookmarks and tabs in one. This is thought about with the new Windows 7 look, but also OSX's and many Linuxes; Windows 7 being the new, most advertised one, it is the one we see most, and thus think most about. This dock would enable bookmarks to be pinned to the 'tabdock' and then pages could be opened straight from it, with a fading or sliding style animation, so as to make the movement fluid and virtually connect the bookmark and the tab.
The docked tabs would be smaller than the loaded tabs, making it easy to fit more, and visually separating them from the rest. In my mind pops up that addon I used to like, before I completely removed the bookmarks from my Firefox: Smart Bookmarks Bar, which can be found here: https;//addons.mozilla.org/en-US/firefox/addon/4072. It was an effective way to fit more and see less, but still have (nearly) the same amount of information.
But then if you compare that with an application dock bar, you realise the giant difference between both: the web is dynamic and has plenty of pages you might want to access, while a desktop application is more static and can be accessed within one window. Fitting the web in a dock bar suddenly seems more difficult than fitting an elephant into a 2CV. But then again, a feature of Win7's taskbar (which might be present elsewhere, but I haven't bothered looking) can be applied here: what about making docked tabs for websites, and regroup bookmarks as one... that's something to explore later.
Quickly, a crude mockup, with the docked tabs at the right [G (Google), M (Mail)], and the loaded tabs to their left, and then the '+' tab.