As of Mathematica 7, ChebyshevDistance is superseded by ChessboardDistance.
As of Version 6.0, GraphicsSpacing has been superseded by the general option Spacings for GraphicsGrid and related functions.
As of Version 7.0, HistogramCategories has been superseded by an optional argument hspec for the built-in Mathematica function Histogram.
As of Version 7.0, HistogramScale has been superseded by an optional argument hspec for the built-in Mathematica function Histogram.
As of Version 7.0, DesignMatrix is part of the built-in Mathematica kernel.
Regress
(Obsolete Linear Regression Package Symbol) As of Version 7.0, Regress has been superseded by LinearModelFit.
As of Version 7.0, NonlinearRegress has been superseded by NonlinearModelFit and is part of the built-in Mathematica kernel.
As of Version 7.0, AdjustedRSquared has become a property of LinearModelFit.
As of Version 8.0, QuantilePlot is part of the built-in Mathematica kernel.
As of Version 7.0, GradientFieldPlot has been superseded by VectorPlot.