Many countries have allocated small sections close to 5MHz for amateur use. In the UK, these sub-bands are available only by NoV. At the WRC2015 it is possible a contiguous 5MHz band may be allocated worldwide to the amateur community. If this happens, it will be an interesting band but even if it happens it could be some years before it becomes widely available.
Up to now I have only been on 5MHz a couple of times with WSPR with an indifferent antenna with moderate success. I got an NoV over a year ago.