Online browser-based 3D tool to create your own model of a tree, which is fully exportable for common file formats:
SnappyTree is a procedural tree creation app designed to demo webgl and proctree.js. SnappyTree produces proctree.js JSON which can be used to generate trees client side in other web applications/games. In addition, SnappyTree also provides export options for wavefront and collada file formats so the generated trees can be used in other native applications.
You can experiment with this online tool here