Here are a few to choose from: Tree Druid - can be a stand-alone program, or a modeling program plug-in: http://www.zenstar.com/ Onyx Tree Classic or Onyx Tree Pro: http://www.onyxtree.com/index.html Tree Designer: http://free.prohosting.com/~jhubert/TreeDesigner/index.html And this one can be used to spice up the trees after they are rendered: http://www.gardenhose.com/ Hope you find something you like.