ChargeKeep is a simple checkout for selling digital products and services. You'll love how easy it is to accept one-time or recurring payments and manage your customers.
BuiltWith - Find out the technology behind websites
Service Provider Pro - Client Portal Software. Productize your services and turn your agency into a profitable and scalable system.
Wappalyzer - Wappalyzer is a technology profilers and leads data provider. Create lists of websites and contacts that use certain technologies.
MoonClerk - You're just 5 minutes away from accepting recurring payments and one-time payments online. Explore for Free. No credit card required.
What CMS - WhatCMS.org looks at a variety of factors within a webpage to determine what CMS a website is using.
Pabbly Subscriptions - Pabbly Subscription is a recurring billing & subscription management software.