Imperitor wrote this nice grass tutorial on the Blender Artists forums. It goes through the process of making grass in Blender step by step in an easily comprehendible way. This is a good tutorial for anyone wanting to make grass in Blender, or someone new to the particle system.
Towards the end, Imperitor also briefly gives some more advanced tips and techniques covering things like weight paint and curve guides.
This tutorial is not new (it's almost a year old), so don't expect any new posts in the thread to be answered. It's still a nice read nonetheless.