In Jones v. Flowers, et. al, here's the link, the US Supreme Court held that notice concepts of due process were violated by the tax sale of a property when the certified mail notice came back unclaimed and the the taxing authority did nothing to determine the actual location of the property owner or to post the property.
This one's long, but should be read. It has poetential application to code enforcement and other zoning enforcement proceedings that could result in burdens (like liens) on property that amount to a deprivation. It might also apply to downzonings - particularly if they would result in a property becoming non-conforming (the loss of the existing right to an existing use rather than simply a potential future right of use).