American-Israeli Cooperative Enterprise
Jewish Virtual Library: Hannah Arendt
An excellent and thoroughly detailed biography of Arendt's life. Includes philosophical ideas, her relationship with Heidegger, and the establishment of her own important work and career.
Marxists Internet Archive
Marxists.org: "Existence and Being" by Martin Heidegger
One of Heidegger's works that is "easier" to read. Does require some background information, but a good way to introduce one's self to Heidegger and his peculiar writing style.
Other
The Case of Martin Heidegger, Part Two
Second of three. An excellent and thorough treatment of Heidegger's involvement with German National Socialism.
Other
The Case of Martin Heidegger, Part Three
The third and final part of this excellent series on Heidegger's Nazi involvement.
Other
The Case of Martin Heidegger, Philosopher and Nazi
Part One of an outstanding three-part series on Heidegger's involvement with the Nazi party. Seems a level-headed and impartial treatment of a potential explosive topic.
Wikimedia
Wikipedia: Martin Heidegger
Wikipedia offers detailed biographical information on German philosopher, Martin Heidegger (1889-1976 CE).