This page uses OpenLayers to combine Google Maps with OpenStreetMap and the relief tiles from maps-for-free.com.
You can zoom in/out using the controls on the left, or pan the map by dragging it (hence 'slippy map'). If you double-click, it will zoom in and centre on the point clicked. You can also shift/drag to zoom into the highlighted area. You can if you wish resize the window.
You can search for a lat/long coordinate by clicking on the search icon and entering the coordinate. This will create a marker and recentre the map at that coordinate. You can delete these markers by clicking the erase icon.
'Permalink' enables you to keep a particular view (coord/zoom level combination) for future reference, by storing it, adding it to your bookmarks, emailing it, etc.