Basic astable 555 with proper power to run standard red LED at full brightness(18mA) from a 9V source. Modify series resistors and capacitor to attain different high/low times. Control pin capacitor eliminates noise in real life applications.
Make sure to increase observation time to 1sec/1sec to see blinking, default period is about 1.5sec for this setup. Have fun!
A good resource is http://www.talkingelectronics.com/projects/555/Page1-555.html
