Content Studio is a modelling tool designed around X3D and can directly export X3DOM content. Content Studio by Bitmanagement allows for easy and fast creation of 3D scenes and apps through an intuitive interface. With X3DOM support those scenes can be easily exported and deployed to a wide variety of devices like smartphones, tablets, laptops, and desktop computers.
You can download Content Studio here. Also have a look at the developer videos on the same site (scroll down).