Finnegans Wake, Joyce's famously unreadable masterpiece (read it online here), was considerably more readable in one of its earlier drafts. Watch Joyce cross out decipherable words and replace them with less decipherable ones! Watch him end, not with a whimper, but with a slightly less impressive whimper! Sadly, Shem's schoolbook, which in the finished version is a House of Leaves-esque compendium of side columns and footnotes, was not written until much later (according to the footnotes of that section). The introduction to this draft by David Hayman, who assembled it, is worth a read.
Revisionista monitors news websites and detects when articles change. The versions are viewable and the changes are highlighted. Some edits are miniscule, others are quite interesting. A Recommended Revisions list yields all manner of edits. Also on the News Sniffer site, Watch Your Mouth monitors the BBC's 'Have Your Say' website and detects when comments get censored.