Eye of Providence (Regular)
This is that eye in the triangle with the glowy bits on top of the pyramid. It's also known as the "all-seeing eye," and it's supposed to symbolize God watching over humankind. Eyes are religious symbols, and have been for a long time, in a lot of places. Look at the Eye of Horus in Egyptian mythology. The Eye of Providence is part of the back of the Great Seal of the United States, and more or less was the founders suggesting that without either Divine Intervention or luck (depending on which founder you asked), America wouldn't exist.
Eye of Providence (Conspiracy)
The Eye of Providence is a widely-recognized Masonic symbol, but conspiracy theorists assert that the eye is also a symbol of the Illuminati (when they even draw a distinction between those two groups.) But here's a question: if you were running a shadowy cabal that ruled the world in secret, wouldn't you be a little more subtle than putting your logo all over everything?
The Pyramid (Regular)
So, this is tricky, but the pyramid and the eye are actually two different things. You wouldn't be blamed for thinking that the pyramid just had a floaty bit. It's a fair assumption. But it's wrong. The pyramid has 13 rows, likely a reference to the 13 colonies, and it's unfinished because the nation was (and is) a work-in-progress. It's supposed to symbolize "strength and duration."
The Pyramid (Conspiracy)
Unless, of course, you're a conspiracy theorist, in which case having 13 steps signifies "depravity and rebellion." The fact that conspiracy theorists hate the number 13 is really unfortunate, in light of there being 13 colonies. Depravity and rebellion are just, everywhere, man. Conspiracy fans also see the pyramid in Jay-Z's Roc-a-Fella Records hand sign, and assert, accordingly, that Jay-Z and Beyonce are high-ranking Illuminati members. Honestly, that would probably be a big step down in money and influence from where they are right now.
"In God We Trust" (Regular)
"In God We Trust" was adopted as the official motto of the United States in 1956, in the afterglow of McCarthyist moral panic. It appears to have been taken from the fourth stanza of the Star-Spangled Banner. (That's right, that whole big song we play through before sports games has three more verses, just as long as the first one.) The song says, "And this be our motto: "In God is our trust." They just didn't make it official until 142 years later. It had been on coins since 1864, but once they adopted it officially, the also started slapping it on paper money.
"In God We Trust" (Conspiracy)
According to some conspiracy theorists, this is actually an anagram for "Winged Tutors," and indicates subservience to the demon Baphomet, or, as you might know him, The Devil. Leave it to conspiracy advocates to decide that a slogan means literally the opposite of what it says. Baphomet's a huge deal to conspiracy theorists. They do not like that guy.
The Eagle and Shield (Regular)
The Eagle is the symbol of our great nation, a strong and majestic and free and mighty and noble creature. In its right (dominant) talon, it extends an olive branch, but it's totally ready to let loose with those arrows in the left talon if it needs to. It holds a shield bearing red and white stripes for the 13 colonies, and flies the "out of many, one" banner beneath a constellation representing a new nation taking its place in the world.
Fun fact: Benjamin Franklin objected to the eagle, preferring the turkey. He referred to the eagle as a bird of "bad moral character," which is ironic considering that Franklin spent every second possible in France as a "diplomat," "liaisoning."
The Eagle and Shield (Conspiracy)
Well again, the 13 stars, 13 arrows, and 13 leaves on the olive branch set off all kinds of alarms for our, well, alarmist friends. They also find sinister symbolism in the pattern of stripes in the shield, whether it's "putting man above God," or reading esoteric meanings into the red, white, and blue. The Eagle is seen as keeping both the olive branch of peace and the ability to defend ourselves away from us.
Several sites also assert that you can find a hexagram (read: The Star of David) in the outline of the Great Seal, which, A: No, you can't, and B: Eww, that's racist.
Serial numbers (Regular)
Serial numbers tell you a lot. They've recently seen an overhaul, but we can focus on the new bills. The first letter is the "series" of the bill. This number changes whenever the bill design changes - like when there's a new Treasurer, so they have to change the signature. The next letter signifies the Federal Reserve Bank that issued the bill. (This used to be a huge letter in a big circle, but that's gone now.) The numbers and last letter refer to the order in which the bills were printed, which helps you keep track of where the money is going. If you see a star after the serial number, that means it's a replacement note, issued in lieu of another dollar, usually because of a misprint.
Coded messages (Conspiracy)
Did you know that you can fold a dollar bill so that it says "Illuminati?" Did you know that you can fold a dollar so that it "predicts" the September 11th attacks? Did you know that if you twist and distort a message enough, you can make anything say anything else, because that's what happens when you go looking for ridiculous garbage?
Michael Fazio claims that he's found some 3300 symbols on the dollar bill by folding it different ways, and he's not the only one to make these assertions. The problem is that the flips and twists are so ludicrous, and besides - if people really were ruling from the shadows, they probably wouldn't broadcast that fact, even in a method as convoluted as this.