Defcon level can be found here. Click on the yellow Defcon circle and it will show current level.
[EDIT: I archived the page here in case it changes again.]
I haven't checked it in a few days, but we've moved from 5 (lowest) to 4 since I last checked. I've never seen it go above 5. Something is happening.
From this page it explains:
Level of readiness: Increased intelligence-gathering and security measures
Historical Precedent: Sporadically throughout Cold War, War on Terror
[EDIT: I was shocked it had gone up, didn't even read the alert, just noticed it had gone up. Some anons have already posted in the comments that the raising to level 4 has to do with Syria.]
ALERT Alert Increase: Threat Level Raised For United States Military In Iraq In Case Of Retaliation For recent U.S Syrian Airstrikes.