We have seen a lot of different functionalities that Ogre 3D offers, but Ogre 3D also makes it quite easy to extend it with new functions. That's the reason there are a lot of different libraries that can be used to add some new functions to Ogre 3D. We will discuss some of these libraries to get a feeling for what add-ons are out there. A complete list can be found in the wiki at http://www.Ogre3D.org/tikiwiki/OGRE+Libraries.
Speedtree is a commercial solution used to render a lot of good-looking trees and grass. It is widely used by several commercial games and the founder of Ogre 3D Sinbad offers a binding for Ogre 3D. Speedtree and the binding for Ogre 3D must be bought and aren't freely available. More information can be found at http://www.ogre3d.org/tikiwiki/OgreSpeedtree.