I recommend Batch '81 and Kakabakaba Ka Ba (for campiness and musical fun). This reminds me that I still have to submit The Blossoming of Maximo Oliveros to The Auteurs, a personal favorite of mine, and that I still have to watch more Filipino films.
Great to see a list of films from the Philippines, Ishmael Bernal's wonderful "Himala" is also my own favorite. I recently watched "City after Dark" which is a great portray of multiple characters. "Insiang" and "Maynila in the Claws of the Neon" are the likely best Brocka films I've seen so far, but I also liked "Weighted but Found Wanting" which reminded me of Satyajit Ray's "Distant thunder". "Evolution of a Filipino Family" is the current #1 of my want-to-see list ever since I watched his masterpiece "Death in the Land of Encantos" on a local film festival. Due to the length of Lav Diaz's films these seem to have a bad distribution, and some are impossible to find. I haven´t seen any films by Brillante Mendoza, but the trailer for "Serbis" looks interesting.