I think I've posted on here before but http://uksnowmap.com/ is quite neat.
Effectively for twitter users - if you report #uksnow and include your
postcode district (e.g. BR6) and a "rating" out of 10 - very subjective,
obviously, it plots it up.

It's obviously limited to twitter users so will be more towns-and-cities
heavy, but clever nonetheless. I've just changed the settings to show the
last 8 hours' worth of reports and you can see a smear from NW England all
the way down to Essex at the moment where snow is being reported (just
spoke to my friend in Loughton who said her kids were quite excited
now...!)

Richard