Google Maps is usually fine, but sometimes it is more convenient to have an atlas in book form. The larger and more up-to-date the better. We have the Readers Digest Atlas of the World.
http://www.amazon.co.uk/s?ie=UTF8&field-keywords=reader%27s+digest+illustrated+atlas+of+the+world&index=blended&link_code=qs&sourceid=Mozilla-search&tag=firefox-uk-21
http://www.amazon.co.uk/s?ie=UTF8&field-keywords=reader%27s+digest+illustrated+atlas+of+the+world&index=blended&link_code=qs&sourceid=Mozilla-search&tag=firefox-uk-21