UmbracoBooter.cs

///
/// I usually create an UmbracoBooter class to set the dependency resolver and config
///
public class UmbracoBooter : IApplicationEventHandler
{
  public void OnApplicationStarted(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
  {
      var kernel = NinjectWebCommon.UmbracoStart();

      DependencyResolver.SetResolver(new Ninject.Web.Mvc.NinjectDependencyResolver(kernel));
      GlobalConfiguration.Configuration.Services.Replace(typeof(IHttpControllerActivator), new UmbracoWebApiHttpControllerActivator(kernel));
  }
}

///
/// Use this method to get the kernel from Ninject
///
public static class NinjectWebCommon 
{
        public static IKernel UmbracoStart()
        {
            bootstrapper.Initialize(CreateKernel);
            return bootstrapper.Kernel;
        }
}