The National Parent Forum for Scotland have produced new Revision in a Nutshell guides for the new Highers (20 subjects) and updated revision Guides for National 5s.
These guides contain direct links to SQA specimen papers, exemplar question papers plus past question papers, where appropriate. They are designed as digital resources and work well with IPads or other tablets.
New Higher: http://www.npfs.org.uk/new-higher-revision-guides
Nat 5: http://www.npfs.org.uk/national-5-revision-in-a-nutshell