Annotopia is an open-access, open-source, open annotation services platform developed for scientific annotation of documents and datasets on the web using the W3C Open Annotation model http://www.openannotation.org/spec/core/. Using Annotopia, virtually any client application including lightweight web clients, can create, selectively share, and access annotation of web documents and data. This can be done regardless of the ownership of the base objects being annotated. Annotopia supports unstructured, semi-structured and fully-structured (semantic) annotation; manual and automated (textmining) annotation; permissions, groups, and sharing. It also provides access to specialized vocabulary and text analytics services. Annotopia is an open source platform licensed under Apache 2.0.