I recently spent 3 days experimenting with particle systems, materials and lighting, trying to recreate the grass from Big Buck Bunny. This was my result.

In this 22-minute video tutorial, you will learn how to:

* Control particle strands
* Save on rendertimes by using child particles
* Evenly distribute flowers across a plane
* Effectively use the colorband feature
* Make a field of uniform strands appear 'lumpy'

Once you've watched it, check out the bonus tutorial on how to animate it:
blenderguru.com/the-secret-to-creating-realistic-grass/