We've been building https://www.datafragment.com, a tool that can help you get prospects for your product. It lets you search the web's HTML code.
Some of our current users use it to find Wordpress websites with specific versions of Wordpress, others to find websites that use niche-market tools, ones that are not covered by incumbents such as Wappalyzer or BuiltWith. We're currently focused on the French market.
Curious to hear your thoughts, if you are looking for new ways to find prospects.