Hi,

Based on a scene previously modelled for a dry and sunny day, I tried to get a "Just after the rain" fx, giving to the objects a wet feeling. I rendered two images, one with the base diffuse materials and one with a phong version with spec to get the required reflection. I then mixed them with Gimp leting appearing the dry image when required.

Modelled with Blender
Rendered with Indigo 1.04
Postpro with Gimp