Grab a Grid Reference...

Drag the red marker on the left map to where you want a National Grid reference (as defined on Page 35 of A Guide to Coordinate Systems in Great Britain)
(Although the National Grid covers a portion of Ireland Irish grid references are usually given using a different system. Irish grid refs can be obtained here) The grid refs will appear on the right, and corresponding boxes on the map.
Press the Satellite button to turn on the aerial photos, or Hybrid for both maps and aerials.
Use the + and - buttons to zoom in and out, and the arrows to pan.
Please do not record using 2km or 10km grid refs. These are for information only.
To remember a location for future use, right-click over "Link to this location", select "Copy Link Location" (Firefox) or "Copy Shortcut" (IE), paste it into your browser's web address field, then bookmark it. Build your own set of bookmarked locations. You can also paste it into emails, or use in links on a website. (The zoom, aerial and resolution settings are copied too!).
If you find this tool slow and jerky with Internet Explorer, try Firefox, or Chrome or Opera, which are all much smoother and faster on my PC.
Showing boundaries slows the map update process, considerably with Internet Explorer. Turn them off while moving and zooming the maps if you find this to be a problem. Boundary names can be found by clicking on them (unless using IE).