This is a cool technique I picked up on the internet; I do not take credit, as it wasn't me who devised it. I did it in CS4, but I am pretty sure it could be done in older versions as well.

Start a new document - surprise, surprise. Size doesn't really matter. Open up a new layer, and fill it with brown, a nice dirt-brown.

Open up a new layer, and fill it with white this time. Now noise this up. Full effect (400%), uniform, and monochromatic. Now blur it a little bit. Slightly less than 1 pixel, 0.7 did it for me. Change the blend mode to multiply.

Now, a new layer, filled with white, same noise settings as the last one, and same blur. On second thought, you could probably just duplicate the first white layer. Blend mode normal.

New layer, filled with grass-green. Multiply. Merge it down with the second white, noisy one.

Filter-Stylize-Wind. Stagger from the left. Now rotate the image, 90 CW. Use the wind filter again. Same settings. Then rotate it back, 90 CCW. There you have a cool-looking grass. It could be used as a pattern for other purposes, using the Offset filter and the Clone Stamp tool quite easily.

Hope you like it, and as I said, it's not my technique to begin with. I just found it.