Juxta is a free, open source tool for comparing and collating texts, originally intended for comparing multiple versions of the same text. It offers several views and visualization options, including histograms and side by side comparison. Juxta is available as both a desktop application and as a web service that can be integrated into the user's own website.

CollateX is a free Java library for collating texts offered by Interedition, designed to be the successor to Peter Robinson's Collate. It uses a component-oriented architecture, to enable users to mix and match components according to their needs. Though its core library is Java, it also integrates a demo web application, a demo client application and Python language bindings that allow CollateX to be embedded into Python applications.

TUSTEP (Tubingen System of Text Processing Tools) is a free, open source, widely-used toolbox for text processing. It is aimed at scholarly audiences, can work with texts in both latin and non-latin scripts, and is primarily designed for humanites applications. Its modules include data capture, information retrieval, text collation, text analysis, sorting and ordering, rule-based textual manipulation, data export and typesetting. The user manual is only available in German at this time. This tool has been in continuous development since the 1960s.

Collate was a program designed for scholars concerned with the difficulties of medieval vernacular traditions. It aimed to help scholars with the preparation of critical editions, and could collate up to a hundred texts. Collate was also capable of handling marked up text. It was available for Macintosh only, and could be purchased directly from its creator.

URICA! II  (User Response Interactive Collation Assistant) was an interactive collation program for the Macintosh. It semi-automated text collation, and assisted text comparison by 'tagging' variants or automatically reconciling small differences. URICA! II built upon the foundation of URICA!, the first iteration of the program.

DV-COLL (Donne Variorum Textual Collation Program) is a historically important textual collation program first introduced in the 1980s and maintained into the present. It was originally designed to assist in creating a digitized corpus of the works of John Donne, and has been opened to other researchers for collecting, comparing and analyzing the works of other poets.

Trend Miner is a tool designed to enable portable open-source real-time methods for cross-lingual mining and summarizing of large-scale stream media. It combines elements from natural language processing, knowledge-based reasoning, machine learning, economics and political science. It is designed to access and interpret data from sources such as blogs, Facebook and Twitter.

Tesserae is a web-based interface for exploring intertextual parallels. At this stage of the project, it only permits comparison of texts from three curated corpuses, representing selections from canonical Latin, Greek and English literature.

The Juxta family of software (Juxta, Juxta WS, and Juxta Commons) allows you to compare and collate versions of the same textual work. Juxta Commons is an online space powered by the open-source Juxta Web Service that lets you collate sets of two or more texts and share online visualizations of the differences between them. Side-by-side or "heat map" visualizations can be viewed on the Juxta Commons site, while embedding codes are available for sharing a compact version of the heat map visualization on your own blog or website. Collation results can also be output as an XML file with TEI parallel segmentation markup, or as a Word document or HTML file with a base text and traditional textual apparatus. Development of Juxta Commons was sponsored by NINES.

Wikidot is a web application service that allows you to create a traditional wiki, forum, or blog. You can collaboratively work on documents, share files and build and host websites.
Wikidot is also a large community with an active question and answer forum. Although it is free, there is a low cost premium option.