National Grid Reference Redirect is a simple free service that takes your UK Ordnance Survey Grid Reference map location number, and then whisks you to the equivalent string of geo-coordinates on the large public mapping services such as Google Maps. Sadly it doesn’t yet work with the excellent OS-based footpathmaps.com or the historic maps.nls.uk.
Usage: make sure you use the six-number format, e.g. SJ882359. If you have a more precise eight number OS Grid Reference — such as SJ882?359? — then you’ll need to lop off the last ‘?’ number in each block of four, and then cross-reference with the same spot in the OS-based footpathmaps.com and maps.nls.uk to work out the precise spot.
We could really use a Web browser plugin that streamlines all this, and intelligently discriminates between six and eight OS digit map references. Or the big mapping services could just start being able to handle OS map references.