Which Crowd Funding site should I use for my game?

Well if you're anything like Simon Roth, you use all of them.  Steam Greenlight, Kickstarter, and Indeigogo.  Why use just one?  Each game crowd funding site has strengths.  This is a pretty smart strategy.  Of course all projects should link to all others.

Greenlight Concepts
You can put anything up at any stage and use the site to gauge peoples interest in your idea.  Using the Greenlight concept page traffic can be driven from steam to your primary crowd funding site.

Kickstarter
The all or nothing popularity of Kickstarter has a good number of projects going here for initial funding.  Arguably more popular for game design at the moment, but unfortunately only one funding option.

Indiegogo
Different funding options (Fixed Funding and Flexible Funding) allow for more options when setting up a project's funding.

Simon also did something smart with the Indiegogo project.  Being from Manchester U.K. the kickstarter is denominated in pounds.  The Indiegogo however is in U.S. dollars.  Running one project in each currency means that he gets both U.K. and international (we U.S. folks) support.  Noticed the dollar amount on the Indiegogo campaign is set very low.  That's some good crowd funding strategy right there.