The invisible web, or deep web, refers to World Wide Web content that is not indexed by search engines.  This can be because the content is held within databases, or is dynamic content, or is not text or html content.  Some deep web resources which can be useful for government or law research in Australia are:

QUEENSLAND

AustLII case law for Queensland

Office of the Queensland Parliamentary Counsel legislation for Queensland

Ozcase historical land and criminal legislation for Queensland

Queensland Courts some databases available to QLS members; also has judgments, practice directions and the UCPR Bulletin

Queensland Law Reform Commission

Queensland Parliament research publications

Queensland University of Technology LIBRARY CATALOGUE gives full catalogued access to many government digital resources - select the Format eResource within the Advanced Search screen

State Library of Queensland - some online databases for legal research

AUSTRALIA

AustLII case law and legislation for all Australian jurisdictions

Australian government

Department of Foreign Affairs Historical Documents

Govpubs Australian government publications guide

Parlinfo web provides access to the Parliamentary Document Repository of the Australian Parliament

Pandora is a collection of Australian online publications, built in collaboration with nine Australian libraries, other cultural collecting organisations and the National Library of Australia

WORLD

Geneva Conventions

Hague Conventions

United Nations

OTHER DIGITAL RESOURCES

Avalon project historical documents in law, history and diplomacy (US & UK)

BailLII UK case law & legislation

CanLII Canadian case law & legislation

Wayback machine

Google has many additional features for deep searching.  A search can be restricted by domain name

e.g. .qld.gov.au
or
.gov.uk etc

to limit results to government documents from a particular jurisdiction. 

Google Book Search and Google Scholar are valuable sources of digitized materials.

Using the Google cache can also be a helpful way of retrieving older information.