CanTree: Free online tree generator
I was reading the last edition of the BlenderArt magazine, number 32, and there I found an interesting resource for architectural visualization artists using Blender. There is an online tree generator called CanTree that you help you on the task of making 2d textures of trees for your project. The online editor is pretty simple to use, with a lot of parameters to setup how the tree will look like, and then we can generate an image of the tree. All images will be already saved as a png file with a transparent background, which make the file great to use as a texture.
If you didn`t read the latest edition of BlenderArt, I recommend you to read it! There are some great articles about tree modeling with Blender.