Image text: This is also one of only five identified situations in which a vuvuzela is actually appropriate.

For our international readers, "Toot my own horn" is an expression (possibly only used in America) that means to brag about ones self.

Vuvuzela is a noise maker that is native to South Africa and is featured heavily in any World Cup game.  Many vuvuzelas blown (played?) at the same time make a noise similar to that of a thousand bees.

Image text: Replace the pendulums with history students and you'll qualify for a grant!

This is another theme in xkcd.  The ripping of psychology, history and english majors is very common in various comics.

Image text: Also, if you read his speech at Rice, all his arguments for going to the moon work equally well as arguments for blowing up the moon, sending cloned dinosaurs into space, or constructing a towering penis-shaped obelisk on Mars.

Not much to explain here.

Here's the full text of the speech to Rice.

Here's the full text of the 1961 speech to Congress.

Image text: Hey, why do YOU get to be the president of Tautology Clu-- wait, I can guess.

Tautology means to repeat the same phrase twice or two parts of a phrase that means the same thing.  This comic is a take on the repetitive nature of "honor" in the Honor Society.

The answer to the image text would be: I'm the president of the Tautology Club because I'm the president of the Tautology Club.

Image text: I mean, what's more likely -- that I have uncovered fundamental flaws in this field that no one in it has ever thought about, or that I need to read a little more?  Hint: it's the one that involves less work.

This comic is a discussion between two characters, the main character and the Philosophy major who has a goatee.  The image text is an additional comment by the character which the goatee.

The character with the goatee is suggesting that the people of science like the main character are holding firmly to their belief of the theory of special relativity.

This is a stereotypical representation of people such as Philosophy majors who thumb their noses at Phyics majors or other scientific ideas, which thinking that they always have the answers and have thought of a new idea that has never been thought of before.  This is referenced in the image text.

Image text: And now someone drunk and hot stumbles in, one thing follows another, and the next roommate to return home sleeps in the hall lounge orbital.

This is a parody on the Pauli exclusion principle of quantum mechanics that states that no two identical fermions (electrons, protons, neutrons, muons) can occupy the same state.  In the case of the comic, the state is the dorm room suite.  The highest lowest level or state is in this comic is your own bedroom, then next two lower higher states are the next two bedrooms, and the lowest highest state is the couch in the living room.  The image text goes on to speculate that the next lowest higher state would be the hall lounge if the living room itself was "occupied" by a romantic pair.  The Pauli Sexclusion Principle dictates that no two roommates can occupy the same "state" in the case of sexual activity and it dictates the order of "states" .

The pun on the name is that when one person is barred from their room due to the sexual activity of their roomate, this is known as "sexclusion".

EDIT: Also, I'm not quite sure whether or not the drawings of the couples in the rooms are very crude stick figures...