OpenStreetMap
According to ITOWorld's OS Locator vs OSM comparison, the whole of Wales is now above 95% coverage of street names.
This means that their map of Wales is now as blue as David Cameron's fantasy election nights.
Now to fix Scotland and England, and then hopefully there's sufficient data released by OSNI to do Northern Ireland.
Discussion
Comment from chriscf on 29 September 2011 at 19:31
How much of this has come from fieldwork, and how much has come from "correcting" or "adding" names from OS Locator? I've seen more than one person do this around my way. I've probably spotted a couple of dozen streets in Swansea alone where the Locator name was wrong - spelling error, old name, or just plain wrong. That said, I did spot one street in Carmarthenshire where the street sign is wrong (and the residents have been complaining about it for the years since it was installed). I've also spotted a non-existent road, and bizarrely Morriston Hospital (which for some reason has a Locator bounding box smaller than the actual hospital has ever been, and nowhere near the entrance).
Comment from Welshie on 29 September 2011 at 19:52
I never 100% trust OS Locator, there's far too many errors for my liking, hence there's quite a lot of not:name tags, especially with Welsh language spelling. Anyone would think that they were done by someone who didn't speak Welsh, and had never been there.
There are many places where there are no street names on the ground, and the only ways of finding out is by asking locals, or OS Locator. Any good research on this sort of thing uses multiple sources. The local character in the pub isn't always the wisest.
Comment from chriscf on 30 September 2011 at 00:05
So, where did this (v3) come from? Or this (v2)? Or this (v6)? It's just that I know for a fact that there's no way you got those from the signs on the street. Particularly not in the case of the street that doesn't actually exist.