That's the program that i always wanted when i was still doing mod work:
http://www.frecle.net/index.php?show=treed.about
It's really awesome. You can use big textures for the leafs like typical for games instead of using hundrets of single leafs. So its very easy to make trees that are cheap to render.
The program is free for amateur and even commercial work and already comes with some halfway decent textures if you don't have the skills to make your own.
You will also need this 3dsmax importer:
