Like a lot of people, we use kitchen sponges at home for washing pots, scrubbing the stuff stuck on plates before the dishwasher, etc. And like a lot of people, we worry about what's actually living in the cells of those little cellulose critter catchers...
We change sponges regularly out of these concerns, but the reality is that the sponges are probably just as nasty on Day 2 as they are on the day we throw them out. Thus, I love the simplicity (and the chance to prolong sponge life and reduce waste) of this idea from LiveScience:
LiveScience.com - Study: Microwaves Kill Kitchen Germs
OK, the title of the article is a little misleading, its not microwaves that do the killing, per se. The reality seems to be that the heat generated by microwaving a wet kitchen sponge is enough to sterilize it. They recommend 4 minutes to ensure death to even the nastiest, hardest to kill spores. I can say that based on my experience with modern microwaves, 4 minutes on "High" for the amount of water in a normal kitchen sponge is definitely enough to superheat the water (i.e. raise it beyond the normal boiling temperature), which will certainly get it well into critter killing temperatures.
WARNING: Be extremely careful removing the newly nuked sponge from your 'wave. It will be hot, Hot, Hot!
NEW WARNING: Apparently some people didn't twig to the fact that its hot water that does the sanitizing and there were a rash of fires and problems with people microwaving dry sponges. YOU MUST WET THE SPONGE!
Personally, I plan to use a small microwave safe dish for this, since then I can nuke the sponge after the morning breakfast cleanup, set it on the counter, and let it cool back to sub-plasma temperatures while I head to work.