The Big Idea

I just finished reading Greg Holden's Starting an Online Business For Dummies. It had some helpful tips discussing Search Engine Optimization (SEO), merchant accounts, using different means to promote your business (blogs, Yahoo! Groups, eBay Store, website), and generating revenue through Google AdSense & Amazon's Affiliate Program. The question is now....what should I do? I'm pretty proficient on eBay (547 stars to date), but I'm more of an opportunistic seller. I sell things that are in the news (Yankee Stadium's Final Season memorabilia), laying around my house, or things that I get for free. My problem has always been finding the perfect item(s) to focus on that are easy to ship, have a good profit margin, and are in demand. What am I interested in? Sports, traveling, food, and trying new things. The question is - how can I turn that into a business?