We all use a sponge to clean our dishes and clean up in the kitchen (hopefully not the same sponge), but unfortunately this tool can be one of the most unsanitary items in our house. Rather than throw it away, there are ways to disinfect them. Cook's Illustrated is known a 'America's Test Kitchen,' so we'll take their word for it that this is the best way to clean a sponge.
Firstly, Cook's Illustrated recommends using a paper towel or a clean dishcloth instead of a sponge to clean up. But we all know that to green our kitchen, getting rid of or minimizing paper towels (and other disposable paper products) is one of the first steps.
So, to find the best sponge disinfecting method, Cook's Illustrated microwaved, froze, bleached, boiled, washed with soap and water, and ran through the dishwasher month-old dirty sponges. According to the magazine, microwaving and boiling, were the most effective methods, reducing bacteria counts from the millions to an 'untroubling' 1000 CFUs. However, because sponges can burn in a high-powered microwave, the final recommendation is boiling them for 5 minutes.
There you have it, the final word from 'America's Test Kitchen'!
Related:
• Simple Green: Microwave Your Sponge?
• Kitchen Sponges: 5 Tips for Greener Cleaning
(Image: Flickr member blmurch licensed for use under Creative Commons)
100 DIY Ideas for the 3-Day Weekend
Danielle's Charming, Classic Walk-Up
Good Food to Share 
The Big Book of Small, Cool Spaces 
Apartment Therapy Presents 
The Eight-Step Home Cure 
White Enamel Flatwa...
How To Make Perfect Bacon in the Oven
Perfect Summer Cocktail Recipe: Honey Bourbon Lemonade
I like the dishwasher myself. They don't stink when they come out, so I consider it a success! :)
No - I don't use a sponge to clean my dishes, and never have. It's a completely disgusting practise and it makes me gag every time I see someone doing it. I use a plastic scrub brush with plastic bristles, which dries quickly and completely between uses and can be easily popped in the dishwasher for sterilisation.
I use a fresh, clean dishcloth every time, and a separate one to clean the counters. Sponges are just plain gross. And I'm not going to go to the bother of boiling one for five minutes, just to make it "safe". ick.
I can't stand the thought of using sponges, either. I knit and crochet and test out stitch patterns with inexpensive cotton yarn and use them to clean and do dishes -- I've got lots so use a clean one every time. They go in with my regular laundry so extra environmental impact is minimal.
I also have a supply of "unpaper towels" made from birdseye cotton -- they're the approximate size and weight of paper towels and, again, are laundered between uses.
I've a massive stack of microfiber towels which I know, not massively great for the environment BUT, they reduce how much cleaner I have to use and on many things I don't need a cleaner at all, such as light oil splatters on the counter wipe up clean with nothing but water.
These go into the washing machine with everything else, come out perfectly clean, are line dried and the original microfiber towel I brought 5 years ago still looks and works exactly the same as newer ones.
The only problem is they can be a little more effort to get a fresh one wet, but once wet they absorb water, cleaner, oil, dirt easily, rinse easily and they can remove things from say scratched enameled surfaces with ease, never had that happen with any cleaner strong of gentle that didn't require a bit of elbow grease and don't even get me started on cleaning the bathroom shower glass, I live in an area with incredibly hard water, shower has to be cleaned every 2 - 3 days otherwise it looks like fogged glass, little bit of vinegar and it's spotless!
About the microwave option -- it filled our kitchen with sponge-stink! It was almost worth it for the look of WTF-incredulity from my wife.
Now I use a plastic bristle scrubby brush as a first go-over, then the green scrubby for the tough bits.
I'm taking the risk - i zap mine in the microwave for a minute or so.
I think I read somewhere that the dishwasher will get rid of 85% of the bacteria...nothing to sneeze at.
We throw ours in the dishwasher couple times a week. I'll try the microwave on top of it (without leaving it unattended)... We also keep a separate sponge for dishes vs. surfaces, & another one in the bathroom just for that area.
If you wash your white clothes with chlorine bleach, you can throw your sponges in the wash. The chlorine will kill any and all germs. I always use sponges but I never use them for more than one day, sometimes less, without washing them.
Oh, and they go right in the dryer with the clothes.
Course the chlorine bleach then enters our waste water!
I'm with RoseCampion - I have a drawerful of dishcloths and I use a new one each time.
I also have a basket of dishcloths that I use once then toss in the laundry. But I still use a sponge, and I microwave it. I just make sure it's quite wet and only have it in for 2 minutes.
maybe i'm a weirdo, but i find sponges are the best option for cleaning. they're also environmentally friendly. i nuke the sponge in the microwave every so often, and of course have different ones around for different uses. i rinse it out between uses so it isn't sitting in a puddle of its own water.
people should be a little less germophobic - our houses are a million times cleaner than they have been in the past, and the human race hasn't died from bacteria yet!