Here is a link for covering the carpeted dead pedal area with a rubber tread material. It protects the carpet from wear, and provides a slip resistant surface to rest your left foot while driving. Cost is < $8.00.
I'm happy with the results; I have applied this material to both of our Sonics, one a manual trans. 1.4 hatch, and the other a 1.8 auto trans. sedan.
There are numerous sources of this product mentioned throughout the thread, and some pictures of the installation.