Stanford Encyclopedia of Philosophy provides overviews of philosophers and philosophical concepts.
PhilPapers is a comprehensive index of journals, books, and open access archives in philosophy.
Intelex Past Masters offers full text electronic editions of the works of Dewey, Hegel, Hume, Kant, Locke, Nietzsche, and Wittgenstein.
Loeb Classics is a searchable, digital version of the Loeb Classical Library, covering the extant corpus of Greek and Latin authors from the Homeric era to late antiquity, in up-to-date texts with facing English translations.
Philosophical Installations offers over 1500 videos of a philosophical nature (free for non-commercial use). The site is curated by Naomi Zack of the UO's Philosophy Department.