Looks like openstreetmap.org's main slippy map now supports zoom 19 (was previously zoom 18).
Comment from Pink Duck on 5 September 2013 at 14:59
I was pleased to notice that today also. It results in names being displayed beside what were previously only icons and some of the highly detailed areas now become more visible / understandable.
* First item
* Second item
1. First item
2. Second item