My recent work has been partially supported by NSF awards INT-9813854, CCR-0208984, CCF-0429894, CNS-0627338, CNS-0708330; Microsoft Research; a visiting fellowship from the Swedish Emergency Management Agency; a grant from the New Jersey Commission on Science and Technology; a Visiting Fellowship at SRI International (NSF CCR-ITR-0326540, ONR N00014-01-1-0837).