If you go to google.com to search some keyword starting with “how to…”, you may find website ehow.com Starting finding niche market, beside Amazon & Ebay , Google Trends you can use E-How You can see the top 10 eHows at left side menu Browsing each category, you can also find out top 10 articles
market research
Google External Keyword Tool will be replaced by New Keyword Tool (Beta) I checked this new tool and found that this is very useful tool for you when you doing keyword research. You can see this tool during usinng Google Adwords-Keyword Tools or access link below:

