From Jeff Lowder, some good logic defintions:

Shifting the Burden of Proof

The burden of proof is always on the person asserting something. Shifting the burden of proof, a special case of Argumentum ad Ignorantiam, is the fallacy of putting the burden of proof on the person who denies or questions the assertion. The source of the fallacy is the assumption that something is true unless proven otherwise.

“OK, so if you don’t think the grey aliens have gained control of the US government, can you prove it?”

Red Herring

This fallacy is committed when someone introduces irrelevant material to the issue being discussed, so that everyone’s attention is diverted away from the points made, towards a different conclusion.

“You may claim that the death penalty is an ineffective deterrent against crime — but what about the victims of crime? How do you think surviving family members feel when they see the man who murdered their son kept in prison at their expense? Is it right that they should pay for their son’s murderer to be fed and housed?”

Plurium interrogationum (Many questions)

This fallacy occurs when someone demands a simple (or simplistic) answer to a complex question.

“Are higher taxes an impediment to business or not? Yes or no?”

Argumentum ad Novitatem

This is the opposite of the Argumentum ad Antiquitatem; it’s the fallacy of asserting that something is better or more correct simply because it is new, or newer than something else.

“BeOS is a far better choice of operating system than OpenStep, as it has a much newer design.”

Argumentum ad Nauseam

This is the incorrect belief that an assertion is more likely to be true, or is more likely to be accepted as true, the more often it is heard. So an Argumentum ad Nauseam is one that employs constant repetition in asserting something; saying the same thing over and over again until you’re sick of hearing it.

On Usenet, your argument is often less likely to be heard if you repeat it over and over again, as people will tend to put you in their kill files.

Argumentum ad Ignorantiam

Argumentum ad ignorantiam means “argument from ignorance.” The fallacy occurs when it’s argued that something must be true, simply because it hasn’t been proved false. Or, equivalently, when it is argued that something must be false because it hasn’t been proved true.

Here are a couple of examples:

“Of course the Bible is true. Nobody can prove otherwise.”

“Of course telepathy and other psychic phenomena do not exist. Nobody has shown any proof that they are real.”

Argumentum ad Crumenam

The fallacy of believing that money is a criterion of correctness; that those with more money are more likely to be right. The opposite of Argumentum ad Lazarum. Example:

“Microsoft software is undoubtedly superior; why else would Bill Gates have got so rich?”

Argumentum ad Numerum

This fallacy is closely related to the argumentum ad populum. It consists of asserting that the more people who support or believe a proposition, the more likely it is that that proposition is correct. For example:

“The vast majority of people in this country believe that capital punishment has a noticeable deterrent effect. To suggest that it doesn’t in the face of so much evidence is ridiculous.”

“All I’m saying is that thousands of people believe in pyramid power, so there must be something to it.”

Straw Man

The straw man fallacy is when you misrepresent someone else’s position so that it can be attacked more easily, knock down that misrepresented position, then conclude that the original position has been demolished. It’s a fallacy because it fails to deal with the actual arguments that have been made.