CatMDEdit is a metadata editor tool for describing resources, mainly geographic information. Developed by IAAA (University of Zaragoza) and GeoSpatiumLab S.L., sponsored by IGN Spain. Technical details: Java, XML, multiplatform, multilingual.
ThManager is a tool for creating and visualizing knowledge organization models, such as thesauri, classification schemes, glosaries and other types of controlled vocabulary in SKOS format
BibTeXlipse is an Eclipse plugin for managing and analyse bibliography databases. Mainly for BibTeX databases, but will import and export many other bibliographic formats.
It's currently in planning phase.