Creating Trees for use in Source

I’m wondering if anyone could enlighten me by sharing what they know about creating tree models specifically intended for use in Source, Hammer.

Perhaps someone could mention a program that could be used, such as a generator of some sort. Or methods for creating trees in 3DS Max or Maya, modeling programs of that sort.

Any information would be appreciated.

http://www.frecle.net/index.php?show=treed.about

someone linked that a while back.