Flattr is described as 'social micropayment service, that makes it easy for you to "flatter" things on the internet that you like. When you're registered to Flattr, you pay a small monthly fee of your own choosing' and is a very popular app in the Business & Commerce category. There are more than 50 alternatives to Flattr for a variety of platforms, including Online / Web-based, Android, iPhone, Windows and SaaS. The best alternative is Liberapay, which is both free and Open Source. Other great apps like Flattr are Steemit (Free, Open Source), Open Collective (Freemium, Open Source), Patreon (Paid) and Litecoin (Free, Open Source).