I just started playing with MapContrib made by Guillaume AMAT from France. It's a great tool to create dedicated webpages (or apps if you want) for certain tags.
Here I made one for dog parks
You can also allow other people to edit the map data in the way you want. They can change existing data or add new, in this case dog parks
So all nodes that will be added already have have the tag leisure=dog_park.
Another map that I made is for artwork
You can define the content of the popup for each POI, as well as predefine some possible node types and their tags. Here I defined statues and sculptures:
and for statues I defined the 2 base tags tourism=artwork, artwork_type=statue and 2 additional tags that you can fill in to set the artist name and the year the artwork was created
The above 2 links to MapContrib can be used on a mobile device, so you can easily add new dog parks and artwork on the go.
People have already defined a number of POI-themes, but you can easily add your own with a simple Overpass Query. I would say, why don't you try it out yourself and get people mapping missing stuff in your town (or across the world)
You can find some additional information (in French) on the wiki