Being a Catholic country, most of the famous festivals in the Philippines are centered around Patron saints and religosity. But do not be fooled about this information, because festivals in the country also means good food, lots of booze, dancing and merry making. Also, festivals are a year-round event. With 7,000+ islands, each having their own patron saint, means you can island hop your way around the country the whole year through.
Below is a link to provide you with a guide to the Philippine fiestas (tagalog for festival) including where and when they are held.