To find the OS National Grid Ref use wheresthepath, and either use control key with mouse wheel to find your point of interest or click the Binoculars Icon to Enter a Place name, then click the finger pointing hand to give the NGR.
Another way is to use freemaptools but this system is not to accurate as uses the WGS84 co-ordinate system, whereas we should be using OSGB36 co-ordinate system.
MagicMap is another good mapping tool with many different mapping options and overlays.
- Magic – http://www.magic.gov.uk (although this might change following Government reorganisations).
- Wheresthepath – http://wtp2.appspot.com/wheresthepath.htm (OS and web mapping services side by side, brilliant!)
- Streetmap – http://www.streetmap.co.uk/
- Nearby.org.uk – http://www.nearby.org.uk/ (great for co-ordinate conversions etc)