VolumeGrass

Volumetric Grass gives unlimited density of grass with no CPU overhead !
Forum & demos | Documentation PDF | Video
This is complete system for building volumetric grass that can be used on Unity4 Free (DX11 needs Pro license) and Unity5
Consists of grass mesh editor and a special shader that gives an illusion of grass being rendered "inside" the mesh volume.
Grass look is highly configurable, handles directional and spherical wind zones & proper intersections with other objects. You can make your own textures easily using built-in editor. For full feature guide refer to forum thread.
Package requires GPU with SM3.0. Mobile versions are on the roadmap (while shader works quite fast on current desktops). Unity4.5+ is highly recommended for shorter install time.