Hi !
I neither looked for sites, nor know anything about theosophy, but here are a few books about metaphysics :
Aristotle
Metaphysics
Descartes
Metaphysic meditation
Leibniz
Monadology
Heidegger
Being and time
Sartre
Being and nothingness
List ( very ) far from being exhaustive.
I only know the French titles, so the ones I give may be a bit different in English.
