Isoliner is the ArcGIS 9 extension for make grids and points theme with interpolate by Kriging's method.
Kriging. Create GRID and points feature class
by selected source layer and Z attribute.
How Kriging works. Kriging is an advanced geostatistical procedure that generates an estimated surface from a scattered set of points with z values. Unlike the other interpolation methods, Kriging involves an interactive investigation of the spatial behavior of the phenomenon represented by the z values before the user selects the best estimation method for generating the output surface.