Boomboy, all actions for the sake of self-interest is already a philosophy; it was popularized by Ayn Rand and is called objectivism. Though most philosophers don't really take her seriously.

Obviously, everyone wants happiness; it's a link between all humans. But I don't think all actions are specifically for the purpose of self-interest. Genuine compassion puts the interests of others before yours'. Granted, Buddhism says one can obtain enlightenment and happiness, but the key to enlightenment may never be obtained if you seek enlightenment for your own satisfaction. Buddhism essentially teaches the total abdication of one's own self-interest for the interests of others (true compassion) as a precondition to enlightenment. In other words, you've reached enlightenment once you truly don't care about enlightenment and happiness for your own sake, but so that you may be in a position to help others.

Now, I'm sure there are ulterior subconscious yearnings for the happiness of self, as it is biological. But not everything is purely self-interest. Compassion (interest of others before the self) is actually just as biological too. Surely, without compassion, the human race wouldn't have survived its evolution. Just because own 'feels good' when they're being compassionate doesn't mean the motives behind the person were purely in their self-interest (otherwise, it really wouldn't be compassion in the first place, and one wouldn't get the 'reward' of 'feeling good').

I guess what I'm saying is that, to say that people act in their own interests is being obvious. But to say that ultruism doesn't exist is just being naively pessimistic.