I like to use Amazon. I just search for products and test them out.
Also try google shopping, yahoo shopping, go to malls and see what people are buying, new products on display
look around your room and see if you can micro niche the products
Remember the times when a certain printer in your house doesn't work and you tried to figure out what the problem is, but there are no resources on the internet? I think that is where you should find your micro niche ideas, where people can't find answers to certain products or something. I heard you can earn a bit from it... but not a lot though. If you want to earn a lot then you probably will have to dominate a big niche or something.
A micro website about baby booties or baby blankets or Graco strollers for infants might be a micro niche as it's more specialized than the generalized category of baby/babies/baby products
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