First of all, read EML's article to make sure you're comfortable with the electronics. I had a lot of issues getting the 555 timer to reliably trigger the 4017, so used the 9v LED flasher circuit from Bill Bowden's site which worked much better (for me). Use the following component values: R1=10K, R2=100K, C1=0.47uF
I built my circuit on two pieces of stripboard:
1) A long piece with 3 LEDs per channel plus the resistor, capacitor, transistor circuitry than gives the LEDs their 'afterglow' effect.
2) A small piece with the 555 and 4017 which was shaped to fit in an Altoids tin along with a 9V battery.