There are a multitude of ways to research/find a niche:
1. Check out Amazon.com or your local book store for all the Dummies books. Each one represents a specific niche.
2. Whilst still at Amazon (or book store) look out for all the 'How-To' books (great if you want to go into info product creation/aff marketing).
3. Check out the magazine racks in a decent sized book store. I'm always amazed by the titles that are available. Each one has a sizeable readership so as to be profitable and the folks advertising in them are aware they will receive an ROI for advertising in these publications.
4. Pick up a copy of any night school/adult education guide/prospectus. Browse through the many amazing and obscure courses people are interested in (again, great for info product creation/marketing).
5. Make your way through clickbank to see what exists, what sells and what doesn't.
6. Spend time in ebay to see what people are buying. Go through all their categories for an idea of different niches.
7. Any half decent keyword tool is a great way to find out what people are looking for. Inventory.Overture.com used to be a great way to quickly find out what people are looking for on the interwebs. Alas, no more. Try:
- Keyword Elite
- Keyword Analyser
You want a quick overview of whether or not folks are actively looking for what ever niche you have considered. Take note of how many people are searching per month in your category/niche. Also take note of anything related to that particular search.
8. Find out what people are already buying and offer them what they want... or an upgrade of what they want.