I learned about this rice substitute when reading Living Low Carb by Fran McCollough. This was the first low carb book I ever read, and I enjoyed the foodie perspective and the amazing ideas, like this rice.
Take a head of cauliflower, run it through your medium shredding disk in the food processor - the result looks like rice :) The key to riced cauliflower is to be sure that you don't over cook it - then it will be mush - you want it to be cooked but have a little bite so it acts more like rice :) I usually nuke it in a large pyrex measuring cup for 4 minutes or so. Also, I cook it as I need it - I rice the whole cauliflower, then keep raw "rice" in the fridge until time to cook it (unless it's incorporated in a casserole).
The bonus is that a cup of brown rice is 218 calories and a cup of cauliflower rice is 25 calories!