Heidegger's Being and Time is among the most profound philosophical works of the 20th century, but the man retains a controversial image—a cold genius without heart or fellow feeling, and a great capacity to delude himself (despite the centrality he placed on "authenticity" in his magnum opus). One might even forgive his anti-semitism, intellectual support of Hitler, and membership of the Nazi party to its very end, were it not for his perverse lack of an apology or remorse later in life (d. 1976). Indeed, he does violence to the literal meaning of the term 'philosopher', i.e., 'lover of wisdom'. Notably, Heidegger's works also happen to be utterly devoid of ethical concerns, preoccupied as he was with "pure insight".
And insight he had aplenty, leading to a revolutionary new way of thinking about how human beings are related to the world. Interest in Heidegger has grown enormously in recent decades, starting with attempts to rehabilitate him by none other than Hannah Arendt, his former student and a Jew who fled Nazi Germany and later migrated to the US, and with whom he once had a passionate affair (read Mark Lilla's article in the NYRB on this astonishing story—subscription is required; psssst! email me if you want the article's text). But for an overview on Heidegger first, check out this BBC film on his life and philosophy, which also talks about his relationship with Arendt: clip1, clip2, clip3, clip4, clip5, clip6.
Here is an illuminating talk from the early 80s between Bryan Magee and Hubert Dreyfus, a leading Heidegger scholar from UC Berkeley. The conversation traces the roots of existentialism from Husserl, to his pupil Heidegger, to the "brilliant misunderstanding of Heidegger" by Sartre (and his waning reputation), to Merleau-Ponty, to Heidegger's enormous impact on almost every contemporary academic discipline. The talk is spread over five clips: clip1, clip2, clip3, clip4, clip5 (clip1 shown below).
Those interested in further pursuing Heidegger may wish to listen to the full audio of Dreyfus's 2007 Fall course on Heidegger's Being and Time at UC Berkeley (~25 hours of podcast). A good teacher and expositor of Heidegger, his classes seem to be always oversubscribed.
Update: For newcomers to Heidegger, here is Simon Critchley's "plain English" account in eight articles of why Heidegger matters and what his magnum opus, Being and Time, is all about: one, two, three, four, five, six, seven, eight.