Major & Mrs Holt's Battle Map of the Somme Battlefield
Shows;
Modern Roads
Grid Reference system
Location index
Battle lines 1/7/1916
Ground gained 17/11/1916
Bunkers Craters Trenches position
1914-18 Place Names
Memorials
Museums
Cemeteries
Tourist Info

If travelling to the Australian Battlefields see this book, Anzacs on the Western Front which is the best available.