i absolutely love this project. it's amazing,
the only thing i'm a little sad about is that i never wrote the pass plugin i wanted for password store [1]. but hey you can still write one
the main author moved, but there are fairly active forks[2].
the amazing thing about this is that you can write plugins in any scripting language you want. you can pretty much hook it's basically a mighty scriptable version of webkit.
here are a bunch of scripts you can use to extend it with [3]
on a sidenote, a completely different, but also interesting approach are conkeror [4] and luakit [5]. though luakit seems abandoned too. luakit is kind of a lua webkit browser framework with sane vi like defaults. conkeror is an emacs for xulrunner, however keep in mind that since firefox is taking over the role of xulrunner you might not really need xulrunner at all.
[1] http://www.zx2c4.com/projects/password-store/
[2] https://github.com/mathstuf/uzbl/tree/next
[3] http://www.uzbl.org/wiki/scripts