example of a good software design document
Not exactyly an example, but how can I forego the chance to mention the four part series on functional design by our StackExchange founding partner Joel that inspired all subsequent design documents I created:
Painless Functional Specifications - Part 1: Why Bother? http://www.joelonsoftware.com/articles/fog0000000036.html
Painless Functional Specifications - Part 2: What's a Spec? http://www.joelonsoftware.com/articles/fog0000000035.html
Painless Functional Specifications - Part 3: But... How? http://www.joelonsoftware.com/articles/fog0000000034.html
Painless Functional Specifications - Part 4: Tips http://www.joelonsoftware.com/articles/fog0000000033.html
Have a look at the documentation framework unify from eightshapes http://unify.eightshapes.com/, it provides indesign components and templates to allow you to create compelling design documents that you list.
For guidance upon the content of Personas Forrester have an up to date paper that compares personas from a number of well known digital agencies.