It's official - the NYE programme. Probably won't appeal to non Portuguese speakers I'm afraid.
10pm - the final of 'Idolos' 2010 live on stage (Idolos being as I said the Portuguese equivalent of American Idol etc)
12mid - firework display
1215 Diego Miranda - http://www.youtube.com/watch?v=ufOYmVfvG4c
They don't say in this announcement what will be happening on the Saturday night.
The Paderne Medieval festival (knights in armour and all that) runs December 20 - January 2. Paderne's a small village about 6 miles up the road.