"Jefferson lives!"—John Adams' last words (Ironically incorrect, as Jefferson had just died as well)
Thomas Jefferson  is best known for being the guy who wrote the Declaration of Independence. Later, he became the third president (1801 - 1809) of the United States of America and bought Louisiana from Napoleon. He then sent Lewis and Clark out to explore the newly purchased countryside. Jefferson was also known for designing (he was also an architect) the famous estate of Monticello, which served as his home. In fact, he's probably the closest the U.S. presidency has ever had to an Omnidisciplinary Scientist, having also studied mathematics, philosophy, botany, music, archaeology, and several languages (notably French, Greek, Latin, Anglo-Saxon, and Gaelic). Not to mention he also founded the University of Virginia as he couldn't find a university that could handle his terrifying intellect, and his 6,500-odd book collection formed the seed of the current Library of Congress (after the original contents of the Library were burned in the War of 1812). To top it all off, the guy invented macaroni and cheese and the swivel chair - quite probably the sort of chair your butt graces right now!
Jefferson was a champion of small government and agrarianism, something that often put him at odds with some of the other Founding Fathers, most notably Alexander Hamilton, who envisioned America becoming an industrial power. However, in the election of 1800 (which in its inflammatory rhetoric makes modern negative campaign advertising sound polite and genteel), the two were able to put aside their differences long enough to prevent the power-hungry Aaron Burr from entering the White House. Today, Jefferson has become a celebrated figure in libertarian communities for his belief in limited government.
Jefferson also owned slaves. That's right -- the very person who wrote "all men are created equal" was a slaveholder. (Not that that stopped him from being outspoken against slavery... at least, until the Haitian Revolution and afterward. Of course, Your Mileage May Vary on this. It's commonly held that Jefferson produced offspring with Sally Hemings, one of his slaves (who was actually only a quarter black, and his [dead] wife's half-sister), but this has never been proven. The DNA evidence more or less proves that a Jefferson did so, but without genetic sampling it's impossible to tell which one. Jefferson had a lot of relatives, most of which had good relations with the family's slaves, though not necessarily in that way.
During his presidency, the US made its first large-scale foreign interventions in the Muslim world. The Barbary Pirates of north Africa were preying on American ships (formerly protected by the Royal Navy) and Jefferson didn't want to continue paying protection money. So the USS Constitution (Old Ironsides) was sent over with seven other ships, including sister ships USS Constellation and USS Chesapeake and an early USS Enterprise,and a few Marines to persuade Tripoli, Algiers, and Tunis that the young nation was not one to be screwed with (which is the origin of the "Shores of Tripoli" verse in the USMC Anthem)
Thomas Jefferson was an outspoken deist who ridiculed the virgin birth and the concept of the Trinity. However, he believed that Jesus Was Way Cool and created his own version of The Bible by taking a knife and cutting out mentions of the supernatural and what he thought to be other misinterpretations of Jesus' teachings.
Jefferson died on July 4, 1826 -- the fiftieth anniversary of the signing of the Declaration of Independence on July 4, 1776. John Adams, the second president and Jefferson's sometimes-rival-sometimes-Heterosexual Life Partner, died a few hours later on the same day, his last words being commonly recorded as "Jefferson lives!". Jefferson's face features on the US $2 bill.
Sadly, he came to hate the presidency and he had it left off his gravestone. However much he disliked the presidency, history has not shared his opinion. He's generally regarded as one of the best presidents the U.S. has had and frequently tops or nears the top of historical rankings, sharing company with the likes of George Washington, Abraham Lincoln, Theodore Roosevelt and Franklin Delano Roosevelt. His face is one of the four atop Mount Rushmore.
- Arch Enemy: Alexander Hamilton
- Badass Boast: "I have sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man."
- Badass Bookworm: Up to Eleven. His personal library formed the core of the University of Virginia's library when it was founded -- over 6000 books.
- Commander Contrarian: As Vice-President to John Adams. So much so that his term highlighted a flaw in the American electoral process: that having the Vice-President be the candidate with the second-most votes in the Electoral College would likely lead to the President and the VP being from ideologically opposed parties, as the second-place candidate would almost certainly be the opposing party's presidential candidate.
- Magnum Opus: The Declaration of Independence.
- Omnidisciplinary Scientist
- Redheaded Hero
- Renaissance Man
- Vitriolic Best Buds: With John Adams.
- Why Do You Keep Changing Jobs?: Tied into his role as one of America's earliest examples of the Renaissance Man.
Jefferson in fiction
- Played by Ken Howard in 1776 and Independence.
- Jefferson was also one of the several presidents Howard played in the musical flop 1600 Pennsylvania Avenue.
- In HBO's miniseries about John Adams, he's played by Stephen Dillane.
- In the Merchant-Ivory film Jefferson in Paris, Jefferson is played by Nick Nolte with Thandie Newton as Sally Hemings.
- Briefly mentioned in the 90's Batman storyline "Dark Knight, Dark City", where he turns out to have been a demon-summoning cultist before becoming a politician.
- Voiced by Ben Stiller(!) on the PBS show Liberty's Kids.
- In an episode of ~30 Rock~, Tracy Jordan discovers that he is a descendant of Jefferson and Sally Hemings. Tracy then has a Dream Sequence in which Jefferson is played by Alec Baldwin.
- Inspired by this, Tracy tries to self-finance a movie about Jefferson with him playing *all* the roles.
- In The Simpsons episode Mr. Lisa Goes to Washington, Lisa goes to the Lincoln Memorial for inspiration, but it's too crowded, so she goes to the Jefferson Memorial. Jefferson takes offense:
Jefferson: No one ever comes to see me. I don't blame them. I never did anything important. Just the Declaration of Independence, the Louisiana Purchase, the dumbwaiter... No, don't go! I'm so lonely...
- An extremely negative portrayal of Jefferson as a hypocrite who trampled on the democratic principles he advocated appears in Gore Vidal's Burr. Since the book is from Burr's perspective, it also provides a very different portrayal of him than most Americans are familiar with.
- Sort-of example: The Jefferson Memorial is the site of Project Purity in Fallout 3. After activating it, the muddy, irradiated water clears to show his statue standing proudly.
- The film Almost Heroes is set in his administration. The protagonists meet Aaron Burr at a party.
- In the Married... with Children episode "Here's Looking at You, Kid", Bud is supposed to help Kelly study history; instead, he tells her that Jefferson's wife was black, he was "a real Renaissance man [...] an architect and a dry-cleaner" and he wrote "Movin' On Up" (the Theme Song for The Jeffersons).
- The Adventures of Dr. McNinja briefly depicts Jefferson as a time-traveler. With a jetpack.
- Jefferson's early death in 1809 is the Point of Divergence for the Alternate History Decades of Darkness.
- In an episode of Family Ties while working on a term paper about Thomas Jefferson, Alex falls asleep and dreams of being at the Constitutional Convention in 1776 where Thomas Jefferson looks like Alex' dad Steven. Alex gets a job as Jefferson's house boy and ends up helping him decide to write the Declaration of Independence.