[Glice]

Yay! Usually I get to these threads too late, and someone's already tainted your mind with existentialism, which is arse.

If you're not too acquainted with philosophy, there's lots of introduction to philosophy type books which you can pick up to give you a taster of what you might be interested in finding out more about. A lot of people scorn the Begginers [insert philosophy/ philosopher] but I happen to think they're quite useful if you don't want to read, say, Hegel's Phenomenology of Spirit.

There are a few books which have wonderful narratives which suggest or explain a philosophy - for instance, Kierkegaard's 'Either/ or' (or any of his), Nietzsche's 'Thus Spoke Zarathustra' or Camus' 'The Plague/ The Fall/ The Outsider' - I happen to like the former best, but lots of people prefer the outsider.

If you're looking at getting an overview of philosophy 'from the horses mouth' (as it were), then any of these are pretty much indisposable -

Plato - Last days of Socrates; The Republic
Aristotle - The Nichomacaen ethics (sp?); The Politics; The Metaphysics.
Descartes - Meditations
Kant - Critique of Pure Reason; Critique of Judgement.
Hegel - Phenomenology of Spirit
Nietzsche - Pretty much anything by him should give you an idea of what he's about, but you probably don't need the last few he wrote.
Adorno - Negative Dialectics.
*Edit: Sartre - Being and Nothingness
Heidegger - Being and Time

*These last two I really hate but are very important to philosophy. This list is by no means exhaustive, and I'm sure that Atari or some other people here will come and add some that have temporarily slipped my mind.

To be perfectly honest, you should avoid Hegel, Adorno and Kant until you've read quite a bit on the subject - while they are absolutely necessary, you probably won't get them immediately. In fact, if you meet anyone who has read and understood all of Hegel, they're either a liar or a genius.

But the best advice I can give is to read an introduction to philosophy-type book, find out what you're interested in and follow that up. Most of all, don't let yourself be baffled or overwhelmed by the books - I've been studying philosophy for most of my adult life, and I still pick up some books and fail to understand them on first reading.

Or were you looking for people to explain their favourite theories to you? I can wax lyrical about a couple of my favourites if that's what you're after.