Can someone please explain in lay terms the current financial crisis?

What is the current financial/economic crisis about? How did it start? What happened with Freddie Mac, Fannie Mae, Lehmann Brothers, Merrill Lynch, and AIG? Why is it such an emergency to "fix" it? How will the government bailout help, and why is the bailout so controversial? Whose fault is all this? Are we really on the brink of financial collapse, and if so, what does that actually mean? I'm not an unintelligent person, I just do not understand economics, and if anyone could explain it simply, I would so appreciate it!