Freelancer and odesk if you want to outsource. Hard to beat LinkedIn for head hunting talent. One trick I did see was putting a job advert in the developer console of a website so if a web developer is poking around they'll see the message.
Thats a great idea. I've heard of that years ago. I wonder how many positions were filled that sparked from such "Super Secret Spy" or "espionage-like hiring technique" lol