Commentpress is an open source theme and plugin for Wordpress 3.3.1 or later designed to enable readers to contribute comments to each paragraph of a text and display those comments in the margins. Commentpress turns a text into a conversation, whether a blog or a fixed document such as an essay, book or article. It may also be used to add a gloss or annotations to a document. This tool is also available for BuddyPress and BP Group Blog.

The Versioning Machine, now in version 4.0, is a framework and an interface for displaying multiple versions of text, and encodes the text according to TEI guidelines. It incorporates features found in both critical editions and electronic publication, in addition to providing an environment for textual editors to comparatively view the results of their edits. This tool may be downloaded for use on a local machine, or hosted on one's server for web usage.

The brat rapid annotation tool is an online environment for collaborative structured annotation of texts. It can be run in a browser (optimized for Chrome and Safari) or downloaded for local installation. It can be used for a variety of annotation tasks, from identitifying natural language entities to chunking to adding metadata.

The DM is an environment for studying and annotating images and texts. It enables users to link together images, texts, or fragments of images or texts, such as a textual annotation of an image or text. It is aimed at scholars of English and French literature, art history, and musicology, and to work with digitized Old English, Latin and Old French manuscripts, medieval maps and scrolls.

The Domeo Annotation Toolkit was an extensible web application for creating and sharing ontology-based stand-off annotations on HTML or XML documents. Users could add annotations manually, or via the tool's full or partial automation options. It also included functions for controlling access authorization and control for both personal and community annotations.

Digitate is a free, open source application for making notes and annotations directly on an image of a cultural artifact such as a manuscript or a painting. Images can also be grouped into projects, saved for later or exported. This application is only available for the iPad.

WordFreak is a free, open-source tool for linguistic annotation. It is designed to support both human and automated annotation of linguistic data, and learns human corrections of automatically annotated data.

WebLicht is an architecture for creating annotated text corpora. It offers a fully-functional virtual research environment with chains of RESTful web services, each providing a linguistic tool such as format conversion, tokenizing, tagging or parsing. It outputs corpora as XML documents.

ANNIS (ANNotation of Information Structure), now in version 3.4.3, is an open source browser-based visualization architecture designed to annotate complex multilevel linguistic corpora. Now in its second version, ANNIS enables users to concurrently annotate, query and visualize data for syntax, semantics, morphology, prosody, referntiality, lexis and so forth. It also offers support for spoken language and audio and visual annotation.