Nathanael has a good post at The Rhine River on whether Heidegger's association with the Nazi party taints his philosophy. My position, in the comments, is the strong one that it does. It's OK to be influenced by Heidegger -- but only by rethinking Heideggerian thought so that it stands over against Nazi ideology and Heidegger himself insofar as he did not.
I confess I don't understand why people try to deny the connection between Heidegger's philosophy and his participation in the Nazi party; even in later life, when Heidegger tried to play down his earlier association with Nazi ideology (as in the Der Spiegel interview, or in letters to Herbert Marcuse), he still affirmed a link between his philosophical interests and his joining of the Nazi party.
The only evidence we have for the common narrative put forward by Heidegger defenders is Heidegger's own suspect testimony (suspect not merely because he's the one under suspicion and because it's the sort of thing people lie about, but also because we have the claims of some of his friends and colleagues that Heidegger had a bad habit of lying -- Hannah Arendt, one of Heidegger's most important defenders in later life, was very clear about it). The common narrative is, roughly, that he joined in the naive belief that he could provide a philosophy to the Nazi party, became rector in 1933, then "discovered his political mistake," resigned, and lectured from a completely non-Nazi standpoint then on out, moderating his opposition to the Nazis only in order to protect his family. If we set aside Heidegger's own testimony, the picture that seems suggested by the evidence is this: the common narrative is right up to the point of the rectorship; he resigned the rectorship not so much because of resistance by the Nazis to philosophical thought, but primarily because of resistance by the faculty to his zealous promotion of the Fuhrer-principle; after his resignation in 1934, he continued to affirm Nazi values ("the inner truth and greatness of National Socialism"), but successively distanced himself from the actual regime; even as late as 1938 he was working to block the advancement of academics on the excuse that they were "unfavorably disposed to the regime" (in the Max Müller incident); and on the rare occasions in later years when he mentioned the Holocaust, he always trivialized it.
There really can be no serious argument that Heidegger's philosophy was not (at least at one period of his life) Nazi. We can only manage such a claim by gerrymandering Heidegger's thought under the Nazi regime. And I am always very disappointed by the weasely evasions put forward by Heidegger and some of his defenders. There is no doubt that Heidegger was a brilliant man; and there is no doubt that one can learn a great deal from his thought. But people who approach Heidegger need to approach him in a way that does not trivialize the seriousness of the Nazi regime and the Holocaust. It is surprising how many people are willing to do precisely that in order to give Heidegger's philosophy a clean bill of health. There can be no sharp distinction between Heidegger the man and the philosophy he put forward. The one was the Nazi; the other was the philosophy of a Nazi who saw it in one period of his life as the core expression of the true spirit of National Socialism. I have no problem with people who are influenced by Heidegger, or who wish to appropriate Heideggerian themes. But we have a moral responsibility to do so (if we do so) only by purgation. The themes and ideas must become part of a system resolutely against everything the Nazis stood for; yes, and resolutely against Heidegger insofar as he supported the Nazis, and Heidegger's philosophy, insofar as it was adapted to being the philosophy of the "inner truth and greatness of National Socialism". Even at the very most optimistic assessment, Heidegger's association with the Nazis, an association he always depicted as philosophical, show serious and dangerous lacunae in Heidegger's own philosophical views. However one cuts the cake, if Heidegger is to be saved, Heidegger must be overcome.