I've been working on a project to provide an annotation facility for wiki articles, sort of like the "blame" function of your favourite source control system.
I've got a prototype of this with the first 1450 or so articles from enwiki here: http://hewgill.com/~greg/wikiblame/
Moving your mouse over text highlights in yellow all the text that was written in the same revision as whatever your mouse is pointing at. Clicking on text brings up the corresponding revision diff on Wikipedia.
I wrote a bit about how this works here: http://ghewgill.livejournal.com/118086.html
I reckon it would take me something on the order of a couple of years to run this through all enwiki articles on my own machine. Larger articles take a few minutes to process, the largest articles (eg. Anarchism) take an hour or more. I wonder whether there would be any interest in making this function more generally available?
Greg Hewgill [[User:Ghewgill]] http://hewgill.com