Inqlude provides a comprehensive listing of all existing libraries for developers of applications using the Qt toolkit. Inqlude is run by the community and open for contributions.
Qt/C++ RDF framework
Soprano is an open and pluggable RDF resource framework which is build on top of QT4. It provides RDF storage, RDF parsing, serialization, inference, and full text indexing in a nice C++ API. The main target of Soprano are desktop applications as it is being developed as a subroject of Nepomuk, the semantic desktop initiative.