The Determinism and Freedom Philosophy Website
Ted Honderich's collection of resources on this recurring theme.

Existentialism
Entry from the Stanford Encyclopedia of Philosophy.

Society for Laingian Studies
Psychotherapies and theories based on the works of R D Laing.

Sartre Online
"The Ultimate Resource", apparently...

excerpt from The Revolt of the Masses...
...by José Ortega y Gasset.

The Void and Emptiness Site
Explores concepts of the void and emptiness from various perspectives: philosophy, science, art, religion...