Curtis,
The following script worked for me:
import arcgisscripting
gp = arcgisscripting.create()
gp.checkoutextension("spatial")
gp.workspace = "c:/temp/work"
in_raster1 = "C:/sapyexamples/data/inRas1"
in_raster2 = "C:/sapyexamples/data/inRas2"
express1 = "out1 = " + in_raster1 + " + " + in_raster2
gp.MultiOutputMapAlgebra_sa(express1)
A few points to consider when you run MOMA with arcgisscripting:
1. Control output workspace
2. Check out spatial analyst license
3. For MOMA expression, supply the output dataset name on the left side of '='.
Thanks,
Xuguang Wang