At the site computeralgebra.de there are listed different databases (as of 2013-09-29). For some of them we compiled meta information (“finger prints”) in RDF.
A Database for Class Groups and Higher Class Groups (by Maximilian Boy and Gunter Malle).
A Database of Higher Congruences of Modular Forms (by Panagiotis Tsaknias).
A Database for Number Fields (contains a database of number fields up to degree 19 created by Jürgen Klüners and Gunter Malle).