Since watching flash videos doesn't work if there's no sound devices, then why don't we add a virtual audio device?
This solution involves installing a program called Soundflower. Best of all, it's free and open source!
I've been using this program on my MacBook Pro for a while now. I mainly use it if I'm streaming my webcam and also want to stream my music. I output my sound into the soundflower device, then use a program called LineIn (free program by RogueAmoeba) to redirect the device to my speakers.