1. What is it?
The Higgs boson is the name of the particle that is the last missing piece of the puzzle in the Standard Model of physics, the model that explains pretty much how everything in the universe works — i.e. why things have mass and experience forces.
2. Why is it called the "God Particle"?
Nobel Laureate Leon Lederman (above) gave it the nickname because of its importance, and also because it's kind of everywhere and nowhere at the same time? Some people really don't like the name because it makes it seem like it actually has something to do with God.
3. Okay then who's Higgs?
Peter Higgs is the physicist who proposed there was an energy field that occupied the whole universe and that gave particles their mass. This energy field is now called the Higgs field, made up of Higgs bosons. (Remember that thing they're trying to find?)
4. What does it look like?
5. How are they going to find it?
There's this thing called the Large Hadron Collider, the largest and most powerful particle collider in the world, that is essentially a giant underground circular tunnel (about 17 miles.) Physicists use it to smash protons into each other, because when they collide there's a very tiny flash of energy that sometimes contains a Higgs boson (one collision in a trillion.) Oh and it lasts for like a fraction of a second, that's why it's REALLY hard to find.
6. So, uh, why is it such a big deal?
If it exists, it "would be the greatest advance in knowledge of the universe in decades." It will confirm that everything we're comprised of has mass — without it, we're all just massless, meaningless particles floating in space, or something.
7. Oh man! So did they find it?
They accidentally announced its discovery yesterday, but CERN (the place where all that particle colliding has been happening) made an official announcement this morning in Switzerland saying their latest experiments show "strong indications for the presence of a new particle," which could be the Higgs boson. But maybe not.
UPDATE: Physicists are pretttyyyyy sure they've found it — about 99.99994% sure — or at least something that looks really similar to the Higgs boson. "I think we have it," said CERN director Rolf-Dieter Heuer. Reassuring.