Ok. I am an atheist, and have therefore investigated my own beliefs pretty thoroughly. I believe that the Universe was not created. According to the laws of physics, neither matter nor energy can be created nor destroyed, so I believe the whole thing to be sort of timeless. Kind of like (I think) you see God, so in a way, we're in agreement to a degree. Then came the creation of the Earth. At some point, the Big Bang, or a similar event occurred. I don't believe the Universe was always a tiny spec - I believe it became like that and the massive amount of energy from all the matter and antimatter colliding exploded it all again.
So bits of matter went flying off into the infinite reaches of the universe. Slowly, they drew together due to gravity to form systems, which joined to become solar systems, which in turn joined to become galaxies.
The earth was one of these planets, and by absolute chance, had the right conditions to form carbon based life. I'll expand a little.
(Raeann95 - this is for you, seeing as you are a little deluded as to the scientific explanation - I'm not saying you're wrong in your beliefs, just incorrect as to the nature of ours, which may or may not be right. I'm not prejudiced or pushy, so don't flame me please)
Someone (I forget who) said that if an infinite number of monkeys sit at an infinite number of typewriters for an undefined period of time, eventually one of them will come up with a script for Hamlet. It's kind of like that. When (I believe) the Earth was formed, 4.6 billion years ago, it was inhospitable. I imagine it is a bit like you see hell. Incredibly high surface temperatures, magma pouring out of the ground, and volcanoes forming left right and centre. This went on for quite a while. When the earth cooled, there were a lot of gases left over, but the most were in the form of water vapor, ammonia, methane, CO2 and Nitrogen (off the top of my head), and these reacted to produce amino acids (relatively complex compounds). These amino acids then became protein molecules, which grew more and more complex until these molecules could reproduce. Reproducing proteins grew to form single celled organisms (organisms that have all of their substance jumbled inside one cell - these include bacteria) and eventually became simple multi celled organisms. This is where my knowledge grows a bit hazy, but if I remember correctly, the primordial seas (highly saline bodies of water that covered the surface of the Earth) had formed significantly before this point and the multi celled organisms evolved into primitive fish.
These fish slowly became amphibians, and crawled out onto the forming land, where (I won't go into Darwinian Evolution right now) they eventually evolved to become dinosaurs.
The dinosaurs were wiped out by an unknown natural phenomenon (an asteroid is the main theory I think) and were replaced with a new group of animals: Mammals. Early primates evolved into modern apes, and another branch evolved into homo sapiens (humans).
That is a pretty simple explanation, but you won't find it hard to find info on Darwinian Evolution (don't bother looking up Lemarcian Evolution - as far as I can tell, no-one thinks Lemarc had it right) and most other topics are easily researched. I hope this answered your question.