Excellent routeplanner giving you directions and map of how to get from A to B.
Interactive map - you can search by postcode, place, grid ref, county, government region, latitude or longitude! You can zoom in on a very small area. All sorts of useful tools.
Via Michelin route planner – can plot a route in Europe as well as UK. It is a nice simple planner and included traffic.
Get A Map – free mapping service from Ordnance Survey. You can search for maps anywhere in the UK simply by entering the place name, full postcode or National Grid reference – and print the maps or copy them.
Excellent map finder – just type in your postcode or a street name.