A good niche is must for running any business online. Finding a new niche is harder these days. Almost all popular niches are saturated. Here are some ideas to research for new niche. Amazon: Amazon is a great tool to research your niche. With lots of categories you can find your niche here. Ebay: Researching niche at Ebay is similar to Amazon. But it has a feature called Puple which lets you know the hot selling products at ebay. A hot selling product may be a hot niche. you can get ebay pulse at http://pulse.ebay.com/ Magazines: You can get your niche from magazines too. You can get list of magazines at www.magazines.com Niche A Week: This is for Lazy people. You'll get a new niche posted every week with its Highest CPC and long tail keywords with search count. You can also discuss about the niche here. You can also use nicheaday to get new niche everyday to your email. But you cannot discuss about the niche with others here. Post if you have any other ideas to research new niche.
Though never used it on big scale, but Google Trends -http://www.google.com/trends can also be used for niche reasearch