What are Your Favorite Crowdsourcing Sites for Graphic Design?

What works best for you in using crowdsourcing for graphic design such as logos, stationery, brochures and websites?

Do you use design competition sites such as 99designs, CrowdSpring, or DesignCrowd, and if so which one is best?

Or do you prefer to use services marketplaces such as Odesk,, or Elance for your design tasks?