Using c# Growl connector library, accept notification parameters via querystring and fire off to Growl.
I'm personally using it to have my Vera 2 (www.micasaverde.com) send growls when things happen.
Growl Libraries: http://www.growlforwindows.com/gfw/developers.aspx
Example: http://192.168.1.135/GrowlWebBridge/default.aspx?Title=Thermostat&Text=Mode+Change+To:++Heat&App=VeraNotify
Install/Deploy:
Create a folder off wwwroot, create application in IIS and publish to that location.