Dilogarithm identities for the central charges and conformal dimensions exist
for at least large classes of rational conformally invariant quantum field
theories in two dimensions. In many cases, proofs are not yet known but the
numerical and structural evidence is convincing. In particular, close relations
exist to fusion rules and partition identities. We describe some examples and
ideas, and present some conjectures useful for the classification of conformal
theories. The mathematical structures seem to be dual to Thurston's program for
the classification of 3-manifolds.Comment: 14 pages, BONN-preprint. (a few minor changes, two major corrections
in chapter 3, namely: (3.10) only holds in the case of the A series,
Goncharovs conjecture is not an equivalence but rather an implication and a
theorem