The Greater Earth Manifesto
- A strong statement on the human space imperative by a group of European organizations.
- http://www.greaterearth.org/ge_manif.htm

Death and Time Travel
- Essay, with interesting illustrations, on suspended animation as a route to colonizing the stars.
- http://nobeliefs.com/death&timetravel.htm

Interstellar Ark
- An analysis of methods for interstellar travel, with a focus on perhaps the most realistic option for success - a large vehicle capable of sustaining thousands of inhabitants for hundreds of years.
- http://strangepaths.com/interstellar-ark/en/

D. J. Tamm: Tsiolkovsky's Imperative in the 21st Century
- Masters thesis on the role of space development and colonization in transforming western society.
- http://www.hudsonfla.com/tsiolkovsky.pdf

The Preparation: Space Colonization
- Detailed discussion by Rex Stephens about his book on the need for space colonization, asteroid mining, and transhumans.
- http://thepreparation.com

Space Quotes to Ponder
- Over 100 brief quotations explaining why expansion of civilization into space is essential to the future survival and evolution of humankind.
- http://www.sylviaengdahl.com/space/quotes.htm

The Political Economy of Very Large Space Projects by John Hickman, Ph.D.
- Explanation of why large space projects (such as solar power satellites, O'Neill colonies, etc) will necessarily be government funded public works, at least at first, rather than created through pure private enterprise.
- http://www.jetpress.org/volume4/space.htm

The Space Review: The Space Flag
- Article by Michael Huang suggesting a new "space flag" as a rallying point for human colonization of space.
- http://www.thespacereview.com/article/438/1

The top Three Reasons for Humans in Space
- Short manifest for space colonisation.
- http://www.thespacereview.com/article/352/1

Sagan's rationale for human spaceflight - The Space Review
- Essay describes space scientist Carl Sagan's thoughts on why human flights to space should continue.
- http://www.thespacereview.com/article/261/1

Spaceflight or Extinction
- Manifest page with links to scientists advocating space colonization.
- http://www.spaext.com/

Space and survival - Wikipedia, the free encyclopedia
- Encyclopedia article on the relationship between the colonization of space and the long-term survival of the human species.
- http://en.wikipedia.org/wiki/Space_and_survival

Why We Do -- and Must -- Go Into Space
- Essay by Jeffrey Liss of the National Space Society, on the many reasons behind our drive to do things in space.
- http://www.nsschapters.org/policy-cmte/files/WHY-JGL_302.pdf

Our Future in the Cosmos
- Essay by Isaac Asimov about the need for the future settlement of space.
- http://www.wronkiewicz.net/asimov.html

NSS Policy Committee: Position Statements and Alerts
- Collection of statements on space policy, including essays on colonization and use of space resources.
- http://www.nsschapters.org/policy-cmte/topics.html

Letters from the National Space Society
- A collection of letters in support of space exploration, sent to and published in newspapers and other media around the world.
- http://www.nsschapters.org/letters/

Solar Power Satellites
- A brief essay on Solar Power Satellites, a key element of O'Neil's High Frontier program
- http://nothingisperfect.home.comcast.net/2004/02/07

Space and Human Survival (Sylvia Engdahl)
- An essay by science fiction author Sylvia Engdahl on why colonizing space is essential to human survival.
- http://www.sylviaengdahl.com/space/survival.htm

National Space Society: Statement of Philosophy
- Vision of "people living and working in thriving communities beyond the Earth".
- http://www.nss.org/about/index.html#philosophy

Foreign Affairs: A Hopeful Future for Mankind
- Louis J. Halle, formerly of the U.S. Department of State, writes in Foreign Affairs (Summer 1980) that space colonization will protect humanity in the event of a global nuclear war (subscription/payment required for full article).
- http://www.foreignaffairs.org/19800601faessay8146/louis-j-halle/a-hopeful-future-for-mankind.html

A Million Reasons to Go To Space
- Brief thoughts from dozens of (mostly) NY space activists on why we need to be in space.
- http://nssnyc.org/amillionreasons.html

Top Ten Reasons to Inhabit Outer Space
- Report from the news service space.com about experts' opinions on why we should colonize space.
- http://www.space.com/scienceastronomy/solarsystem/tenreasons_lead_000723.html

The Top 3 Reasons to Colonize Space
- SPACE.com asks Freeman Dyson and two other space-colonization enthusiasts why we should go beyond our home planet.
- http://www.space.com/missionlaunches/colonize_why_011008-1.html

Space Colonization and SETI
- Interview with Gerard K. O'Neill by John Kraus of COSMIC SEARCH.
- http://www.bigear.org/vol1no2/oneill.htm

Syliva Engdahl on space
- Essays, quotes, and a radio interview from science fiction author Sylvia Engdahl, about the importance of expanding beyond Earth.
- http://www.sylviaengdahl.com/space.htm

Colonies in space may be only hope, says Hawking
- Interview with Britain's Daily Telegraph in which eminent cosmologist Stephen Hawking warns that the human race is likely to be wiped out before the millennium is out unless we set up colonies in space.
- http://news.telegraph.co.uk/news/main.jhtml?xml=%2Fnews%2F2001%2F10%2F16%2Fnhawk16.xml

The Case for Space Colonization Now
- Detailed argument for space colonization by Oscar Falconi.
- http://www.nutri.com/space

Bioterrorism May Spur Space Colonies
- Plans to save civilization by sending people and important documents into space in a 21st Century "Noah's Ark" might get a boost from fears of bioterrorism.
- http://www.space.com/scienceastronomy/generalscience/colonize_now_011030-1.html