Someone just pointed my to Ubiquity, which is a Firefox extension offering an alternative way of issuing browser commands, using a kind of command line. At a quick glance it looks quite promising.
There are several interesting aspects to it, but I don't want to go into all of them. The one that definitely stands out is that these people seem to have realized something very fundamental: Textual command interfaces can be more efficient and intuitive than the ubiquitous (pun intended) point-and-click interfaces. Woohoo!
