Juxta is an open-source tool for comparing and collating multiple versions of a single textual work. It can be accessed through the web at juxtacommons.org, through a desktop application at juxtasoftware.org, or through a subscription for advanced collating at juxtaeditions.com.
The software allows users to set any of the variations of a text as the Base Document for creating a Scholarly Edition. Users can also add or remove versions, change the base text, annotate comparisons, and save the results.
For more information on this process, see the videos on the "My Desk" part of your account.