If you are anywhere on the left of the political spectrum there are many conspiracy theories. Of course it is rife with many of those medical ones (like those about vaccination).
But one consistent annoyance are the ones about 9/11. From loose change to free falling to the color of smoke, many people will not give it up. We get it, you don't like Bush or Cheney. None of us do. There is a distrust of government. Eternal vigilance is a must. But to embrace baseless, evidence free position is just stupid.
Cockburn at Counterpunch wrote a good piece looking at the lunacy and its impact on the lefties. The site also has some good articles looking at the science and facts disproving many theories about 9/11.