  Weak vector boson fusion provides a unique channel to directly probe the
mechanism of electroweak symmetry breaking at hadron colliders. We present a
method that allows to calculate total cross sections to next-to-next-to-leading
order (NNLO) in QCD for an arbitrary V* V* -> X process, the so-called
structure function approach. By discussing the case of Higgs production in
detail, we estimate several classes of previously neglected contributions and
we argue that such method is accurate at a precision level well above the
typical residual scale and PDF uncertainties at NNLO. Predictions for cross
sections at the Tevatron and the LHC are presented for a variety of cases: the
Standard Model Higgs (including anomalous couplings), neutral and charged
scalars in extended Higgs sectors and (fermiophobic) vector resonance
production. Further results can be easily obtained through the public use of
the VBF@NNLO code.
