STOP DRIVING THE VEHICLE!!! Flashing check engine light means you are damaging the emissions system like the catalytic converter when you drive it. Call Jon at Dublin Auto to schedule time for him to diagnose the misfire codes and make some recommendations. He's at (925)828-0243.
As Hal Mentioned, those codes are misfire codes. The 301 & 306 means your computer sensed that the car had a misfire in the #3 & #6 cylinders, and the 300 is a 'random' code that comes up any time any misfire happens. Unfortunately, Hal is also correct that misfires often cause damage to your cars catalytic converter/s (an emissions part included in the exhaust system) but we may not know for certain right away. My shop is in Hayward, if that happens to be more convenient to your location, and we would be happy to check out the cause of your misfire for you, just give us a call or e-mail. The shop name is P R Motorsports #510-786-0851 and our web address is www.prmotorsports.com Hope your day gets better!