You can use the Health Insurance Marketplace to enroll in health care coverage under the Affordable Care Act ("Obamacare") beginning October 1, 2013. Here are some resources to help you in this process.
Health Insurance Marketplace Application Checklist (PDF) 
Get a checklist of the information you need to have ready in order to sign up for coverage.
Healthcare.gov: Welcome to the Marketplace 
This is where you go to sign up for coverage.
How to find the health insurance plan that's right for you 
Gives a brief explanation of the four categories of plans (Bronze, Silver, Gold, and Platinum), plus six things to know before choosing a plan. There's also a 2-minute video that's a simple explanation of what the Health Insurance Marketplace is.
"All Topics" from Healthcare.gov 
Answers to all kinds of questions about the Health Insurance Marketplace