There are plenty of crazy conspiracy theories out there. Here are a few of them that I feel top the list. It's almost amazing to think that some people out there actually believe this stuff.
The Moon Landings
First off, not only is there no evidence whatsoever that the moon landings were a hoax, we can actually prove that it happened at any time. You see when the astronauts landed on the moon, they left some mirrors on the surface which are pointed at Earth. Anybody can shine a powerful laser at any of these mirrors and detect the number of photons that reflect off of the mirror and come straight back to earth.
HIV/AIDS is man made
There are a few crazies out there that claim that HIV/AIDS was created in a lab as a biological weapon or to ethnically cleanse certain races and cultures. Science and rational thought both say that this theory is just plain insane, and that clearly it originated in non-human primates.
This is one of the biggest ones, that UFOs are real and have visited Earth. If a certain former President of the United States couldn't keep secret the personal relations he had with his staff do you honestly think that the government could keep something this huge under wraps?
Now don't get me wrong, I believe that alien life has to exist out there in the universe, there are over 100 billion stars in our galaxy alone, and over 100 billion galaxies in the observable universe. This said, I truly think that aliens have not visited Earth (yet).
Some of the crazies out there think that there are secret societies that are trying to create a one-world government.
What advantage would any governing body gain in creating a central government to rule the entire world. What makes our species strong is diversity, and having a single world government could very easily destroy all that makes us human.
9/11 was an inside job
Really!? Do you really think that the US government has the capacity to keep something this big under wraps, or that they would even want to in the first place. Clearly the US isn't gaining economically from the conflicts in the middle east that have sprung from this world changing event. Except for Halliburton contracts, nothing good has come from 911 for anybody involved.
The world will end in 2012
The Mayan calendar ends in the year 2012, so many people thought that the world would end on December 21, 2012 with a cataclysmic event. This has gone as far as fueling the story lines for a few big budget Hollywood movies. Common sense tells us that nobody can predict the future and there is almost no way of knowing when an earth altering event such as a huge asteroid or comet striking our planet will occur. Guess what, 2012 has come and gone, and the worls is still here.
This one is just plain weird... Google it, there are really crazy people out there that actually believe with absolute certainty that an alien reptilian-humanoid species rules the Earth. Apparently George W. Bush is one of them.
Some of the hardcore Christians believe that there is an upcoming date that all of the true "believers" will ascend into heaven and all of the "non-believers" will stay on earth and face many years of "hell on earth". Numerous Christian leaders over the years have actually pegged this event happening on specific dates, and SUPRISE! all of the previous dates have gone by and nothing has happened.
The sad thing is that many people have been convinced that the rapture was actually going to happen and ended up giving away all of their personal wealth to the church and it wasn't given back to them.