I found a television series on BBC that I've been enjoying lately -- "How Clean is Your House?" It's a very humorous look at dirty homes, and typical of reality TV, the homes they feature are really super filthy. What I enjoy the most is that the hosts (hostesses, if I may be sexist) give some great tips on cleaning, especially with natural products.
A few weeks ago I watched an episode where they used lemon, water, and dish soap to clean the inside of a really dirty microwave. I tried it last week and wanted to share -- it was such an easy clean, and so simple. My microwave wasn't nearly as dirty as the one they cleaned on the show, but it did have some splashes in it -- my husband and children just refuse to cover their food!
Place a cup or so of water in a microwave-safe bowl. Squeeze the juice of a lemon into the water (the lemon isn't crucial to the cleaning, but it does deodorize). Place the bowl in the microwave and heat on high for several minutes. I think I ended up doing it for about 6 minutes, but watch your water so it doesn't all evaporate. I just cooked it until it was almost gone.
After the water evaporated, take a soapy dish cloth (just regular dish soap) and wipe out the mess. Any splashes will have softened greatly from the water and should wipe right out.