Here’s how to get other people to do some keyword research for you.
Step 1: Install a do-follow plugin
This lets people who comment on your blog get a little SEO benefit from doing so.
Step 2: Put your site into a do-follow directory
This lets you be found by the people who use automatic comment submission programs.
Step 3: Use comment moderation
Set it up so that comments are moderated until a person gets one approved comment, then comments from that person bypass the moderation queue.
Step 4: See what keywords people are using
A good percentage of the people commenting, and all the people using automatic commenting programs, will keyword stuff their name in their comment. Presumably, they’ve used that particular keyword because they’ve done some research and decided that there’s a market for it.
Collect a couple dozen keywords this way, and head over to Google’s Keyword Tool to see which ones look like the best ones to create a Neglected Niche Site about. Create the site, promote it a bit, and then do the next.