The OpenStreetBrowser is an application to 'browse' through the information in the displayed part of the map. The aim of the project is to provide a highly dynamic map that makes every mapped feature easily available to the user.
-> go to OpenStreetBrowser
It uses the Overpass API to access the map data.
OpenStreetBrowser shut down its service in 2016 and was reborn in July 2017 with a new implementation. Check the old project site for the previous version.
If you want to create categories yourself, check this howto.