A visa summary can be useful at the early stage of planning a trip. For example a long distance overland journey may be simpler to arrange if most of the route passes through countries that you don't need to get a visa for. However these lists are difficult to keep up to date, and as a summary, they may miss some details which apply to your particular situation.
We don't have a summary here, but see this article on Wikipedia: Wikipedia:Visa requirements for European Union citizens. There are also Wikipedia articles for citizens of particular countries, see Wikipedia:Category:Visa requirements by nationality.
The IATA Travel Centre has a searchable database of entry requirements for many counties based on your passport etc.