Blender 2.5 Python Extrude with Vector

import bpy
from mathutils import Vector

myVec = Vector((1.0,2.0,1.0))

bpy.ops.mesh.extrude_region_move(MESH_OT_extrude={"type":'REGION'}, 
                                 TRANSFORM_OT_translate={"value":myVec})

If you execute this script while in edit mode, with a face selected (in face selection mode) -- then the created faces along the extrusion will/may appear inverted, they revert to outside as soon as you perform other operations on a mesh. Experiment!

The 2.6 equivalent code

The best way to figure these things out is to use the reporting console, (ie, set for example a timeline window to display the information window, any user interaction will show up as code)