Here's a neat little kitchen tip: tired of smelly kitchen sponge (but don't want to buy a brand new one)? Wikimommy has the solution: Microwave it!
First, rinse the sponge and squeeze it as dry as you can, repeat this process twice. Then you put the squeeze-dried sponge (which is still a bit moist) in the microwave, put it on high for about 5-10 seconds maximum. Take the sponge out with care unless you want to end up with a sponge-print on your hands. Run it through some cold water and oh the sweet smell of clean sponge!
http://wikimommy.net/2011/03/07/smell-smelly-sponges/
Human beings are surrounded/covered/internally infested with billions of bacteria all day long. Mediating those bacterial colonies is our immune system's job...And the immune system needs to be used and fight bacterial colonization to become strong.
Unless you have an immune system disease like HIV or are taking immunodepressive drugs for organ transplants...You really don't need to worry about dirty dish sponges.
@pianoarthur, well then you're doing it wrong. =) Sponges get funky b/c you don't rinse them out sufficiently before putting them in the drainer to fully dry.
People (don't know if that's you or not) who leave sponges in the sink all the time and soggy all the time are begging for bacteria to grow unchecked. Ick.
I microwave mine 3 min on high, after rinsing it and leaving it mostly moist. Adding bleach is gilding the lily. I understand running them through the dishwasher works really well too.
A CAVEAT COURTESY OF MY FRIEND:
Do not do this with makeup sponges. Even wet, they apparently become too hot, and will fill up your entire house with burnt rubber smoke. For hours. I still tease her about it to this day.