The following are useful links
Obtaining a passport
http://www.passportsandvisas.com/visas/sao%20tome%20and%20principe.asp
Online Visa Application
http://sao-tome-principe.visahq.com/
Visiting Sao Tome Principe
http://travel.state.gov/content/passports/english/country/sao-tome-principe.html
Becoming a citizen
http://sao-tome-and-principe.travisa.com/
Green Card
http://www.passportcenter.net/requires/o-z/Sao_Tome_and_Principe_application_kit.pdf
Countries which do not require Visa to Sao Tome Principe
http://www.doyouneedvisa.com/passport/Sao%20Tome%20and%20Principe
