Nines project is developing some neat tools. One of the most interesting is Juxta which is a collation tool with a brilliant interface.
It has a histogram of differences between texts.
NINES is a community project around ninteenth century studies.
NINES is a project to found a publishing environment for integrated, peer-reviewed online scholarship centered in nineteenth-century studies, British and American.
Juxta is one of many tools being developed for the NINES community (and others.)
Both are led by Jerry McGann.