Here is a list of (everchanging) myths, or possible myths. Some may count as conspiracy theories:

ADD and/or ADHD exist.

Marijuana is a non-dangerous drug.

Apollo 11 landed on the moon. We are expected to believe this despite many glaring contradicting facts, for instance: NASA faked the first space walk, NASA faked an un-manned moon probe (Gemmi 8?), years after the apollo missions, the van allen radiation belts were discovered to be much thicker than previously thought, and the crew of a space shuttle which to-date is the manned space-craft to have ventured furthest into space (except the apollo moon mission) reported being able to see the radiation with their eyes closed (why didn't any of the apollo crews notice this?)

Evolution. There is overwhelming evidence against evolution, for instance all lifeforms alive today that were also living "millions of years ago" have not evolved. Darwin's survival of the fittest theory is completely disproved by animals that help each other, like birds that warn the rest of the flock when an incoming crow is spotted. While it is better for the group to have that behaviour, individually it is not. That is to say the bird with the selfish gene will outlive the rest because it can still benefit from the other's warnings - but never puts itself in risk by calling out warnings. The theory of Evolution changes more rapidly than I change my socks.

Princess Diana's driver was drunk. Eyewitness accounts and video evidence contradicts so-called forensic evidence.

"Jack the Ripper" killed five prostitutes.

Martin Fleischmann and Stanley Pons' "cold fusion" experiment was a hoax. They had a $40,000 experiment and discovered that under certain conditions it seemed the energy they put in increased - or that is - that they got more energy out than was put in. They said cold fusion was one possible explanation. Researchers have, and continue to reproduce the proven results.

Mentally handicapped Martin Bryant with an IQ of 66, a terrible shot at hunting and no proven experience shooting from the hip, or shooting weapons of such calibre - shot and killed 35 people, crippled two cars and wounded an additional 22 people in the Port Arthur massacre. Bryant killed 12 people all from single headshots, wounded 10 and remained in control, in 15 seconds flat firing just 17 bullets? I do not think so! For one thing, while he may have had rather close targets, shooting people in an enclosed space is something only the best professionals could do so professionally. When you shoot people, they tend to fall, and block other people - and those other people are screaming and running around. Even if no one moved, and no falling bodies blocked other bodies - Bryant would still have had an incredibly hard time shooting 12 people in the head (or neck) in 15 seconds flat. He wasn't even very good at hunting - he was a terrible shot. Bryant - even if he had experience with such weapons, we should expect to be spraying the bullets everywhere in a fit of loonity. However the killer clearly knew exactly what he was doing. Several eyewitness accounts that contradicted the official line of events were discounted.

For instance, in the official version of events bryant stayed at the broad arrow cafe for less than a minute before moving out of it and continuing his killing spree. This is an important fact, because mentally-handicapped people who live in their own world tend to like to move on to other things very quickly. However, there are verifiable witness statements that have the killer waiting (at least) 4 minutes before leaving the cafe. This important because a professional would know that to remain in control he should wait while people outside evacuate, as to eliminate witnesses. There was no incriminating forensic evidence found against Bryant. Well, no forensic evidence at all, unless you count the firearms apparently not planted, but found in pristine condition at his burning house. There is no evidence he owned them, used them or practised with them.

Now there are some tings people will use to incriminate him, like the fact that he was laughing and seemed to be enjoying himself during the trial and while the charges were made against him. However this was not uncharacteristic, for instance his father killed himself by drowning himself in the pond (and had done a lot of paperwork like changing bank accounts to just her name and not his ahead of time to make it easier for her). Now when the police asked Bryant to help search for the body (there was also a suicide note), he was laughing and enjoying himself.

Anyhow to continue discussing any of these in this post would bring but hours of reading for you, so I will go and allow others to comment on these - and other Myths.