I was starting to wonder when this stuff was going to start coming out as I'd heard rumors about stories floating around on the web, but here's a piece from Jewcy detailing the Paul campaign's contributions from hard right, white supremacist organizations. Now, as is noted in the article, Paul's people have not decided yet what to do with some of those contributions, but that alone ought to give people pause. If you want to be the president of the United States of America in 2008, taking cash from the leader of Stormfront probably isn't a good idea.
For more on this, check out Orcinus.
Update: Seems that there's a lot more to this and it sheds a much better light on Paul than the original story.