Bragar and Arnol Community Trust / Urras Coimhearsnachd Bhràdhagair agus Àrnoil has published a wonderfully detailed map of the place-names of its part of Lewis, a labour of love by Anne Campbell, with contributions from many others, over several years. It provides English translations of many names, complete with stories about places. For some, a particular attraction will be the challenge of unravelling the Norse originals that underlie many of the names.
[Note, 09/06/2018: The above website appears to have gone offline. It is quite probable that this would have affected the provided e-mail address too. Web Admin]