Can I land a helicopter anywhere?
Per §91.119 of the FARs, yes. That said, you can't just find an open field-there may be local/state regulations regarding helicopter operations.

14 CFR 91.119:


  (1) A helicopter may be operated at less than the minimums
  prescribed in paragraph (b) or (c) of this section, provided each
  person operating the helicopter complies with any routes or altitudes
  specifically prescribed for helicopters by the FAA