Creating IDW grids of point data for Mapserver

[Cord Thomas]

Hello,

Has anyone experience creating inverse distance weighted (IDW) graphs for
use with mapserver?

I am working in Linux.  I have data collected in PostGIS, some street
centerlines, and would like to calculate IDW raster grids to present in
transparent mode over the street data.

There are two approaches i could use -
1 - calculate the IDW grids as a scheduled process - what tools are there
available to do this?
2 - calculate the IDW grids live given user parameters - though i could
imagine this would be very expensive.

Anyone have suggestions on how to do this?  What tools i might have to do
this?

I see GRASS has some surface calculation methods - I know nothing about
GRASS - can one automate calls to it?

I am interested in open source means only.

Thank you