Prompted by the drawing thread, I'm sure many of use have knocked up maps using various map and WMS providers. I'm currently using the following for a mine/cave map application:
Welsh Lidar
English Lidar
Ordnace Survey via Bing virtualearth (1:50k and 1:25k)
Mapbox Aerial & Road
NLS Old Maps (overview only)
BGS Bedrock, Drift and Linear Features
BGS Soil
Are there any other useful providers for a miney/geology/outdoory application ?