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.

The NeOn Toolkit is an open source environment for engineering ontologies. It supports both the F-logic and OWL ontologies, and its functions include annotation, documentation, ontology evaluation and matching and human-ontology interaction.

RDF Gravity (RDF Graph Visualization Tool) is a free, open-source visualization tool from Salzburg Research's Knowledge Information Systems Group. It supports RDF graph structures and OWL ontologies, including multiple RDF files, and offers a variety of filters for its visualizations.

TemaTres is an open source vocabulary server, web application to manage and exploit vocabularies, thesauri, taxonomies and formal representations of knowledge.