Blockchain technology has prompted new ways of governance and coordination. Such forms receive the name of Decentralized Autonomous Organizations (DAOs). DAOs typically implement decision-making systems to make possible for the community to reach agreements. As a result of the agreements the DAO automatically operates (e.g., hire people, payments, invest in financial products, etc.) by executing code on the blockchain. In the last few years, several platforms such as Aragon, DAOstack and DAOhaus, have emerged to facilitate the creation of DAOs. As a result, hundreds of this new organizations have appeared and are interacting in the blockchain. However, little is known about them. In this paper, we want to shed light on them. We will review the three main platforms (Aragon, DAOstack, DAOhaus) that make possible to create and manage a DAO. We introduce the main differences between these platforms, and we finally compare them numerically. For the comparison we retrieve data from both the main Ethereum network (mainnet) and a parallel Ethereum network (xDai). We analyze data from 72,320 users from 2,353 DAO communities to study the three ecosystems along four dimensions: growth, activity, voting system and funds. Our results show that there are notable differences among the DAO platforms in terms of growth and activity, but also interms of voting results. Still we consider that our work is only a first step and that further research is needed to better understand these communities and to help them to accomplish their aim of decentralized governance.