Why won't my car start?

I was driving the other day and my car was running fine. I stopped at a light and the car just cut off. I didn't even notice until the light changed. After two hours of occasional attempts to start it again, it finally fired up after making a weird noise that sounded like a small firework going off under the hood. It drove very sluggishly and wanted to stall every time I took my foot off the accelerator. When I got it home it idled a little low. It hasn't started since. I had my friend try to start it while I looked under the hood, and white smoke came out of the air intake. Any ideas?