Light Midwest Earthquake

About 10 minutes ago (approximately 5:35 EDT), I felt a light earthquake, which was preceded by an even weaker foreshock. I could feel the entire house move slightly, and heard some rumbling and creaking. One of my brothers called soon after, stating he felt the same thing. Based on this, I estimate it to be about 4.0 on the Richter magnitude scale.

EDIT: Associated Press brief
EDIT 2: USGS map
EDIT 3: Internet reports of activity