Can the 555 IC help me switch between LED's using a DC power source?

[nheugel]

I have a DC power source and 2 LED's. I know they are polarized and only work with the current running one way. I need to swtich between the two electrodes but I am not sure how to design a circuit using a DC source that will switch back and forth at a defined rate. Can anyone suggest either a device or a circuit set up that will allow me to alternate between the two LED's using a DC power source?

 

[schip666!]

Look up oscillators using the 555 integrated circuit, being the very first IC there is probably more information online for it than anything other than Lindsay Lohan.