With the Overture keyword CPC tool down for awhile, I've turned to the Google Adwords keyword tool to figure out the profitability of a niche. To use this keyword tool, enter keywords in the text box. Next, in the field "choose data to display", find the text box that says "Cost and Ad Position Estimates." A new text box will appear for dollar amounts. Enter "5.00" in text box and click on "recalculate." After Google crunches the data, a bunch of keywords with their click values will show up. Any keyword with click value higher than $1.50 has good profit potential. Also, you should do a Google search on the keywords in your niche. Count how many ads show up on the SERPs. If there are ten or more ads, that's probably a sign of a healthy, growing market.
u also need to find out how many searches are made with those keywords. With a higher Click value, the number of searches decreases. So you must factor that in as your market will be considerably smaller. This is coupled with an additional difficulty of marketing your site since it is probably more niche. Just looking at the click value and the ads showing up may seem alittle too simplistic, IMHO
Hmm I would just check how many searches there are and use that for a base of what to build a site about. Only pick something that you yourself are interested in or you might get bored as heck.