Attached Link: http://www.xfrog.com/greenWeb2/Templates/download-xfrog3.html

Full working 30 day evaluation of XFROG- the highend plant making software. NOT easy to learn however- but you can download the nice free plant samples in various formats (not OBJ or 3DS unfortunately)... Also, some new tutorials to help you get started. Interest in mathematics might be useful with XFrog as it is not a simple program to use...