Here's what I've tried: 1) Built a website that let people send USPS (real) mail, from the website. 0 sales. 2) During the social news height, built a digg like

Here's what I've tried: 1) Built a website that let people send USPS (real) mail, from the website. 0 sales. 2) During the social news height, built a digg like social news website with a coworker. Never used by anyone outside of those I work with. 3) Built a custom trail mix website (still running, making regular sales.... barely profitable...). I've been building sites for years, and I'm starting to think that my focus should be on what I'm really good at: C/C++ software (instead of trendy websites). I've been obsessed with the idea of finding an underserved vertical, and taking my knowledge of machine learning and analytics and building some game changing software for that niche. The only issues I have is: what niche?