Freedom for Immigrants

Offers a good history of detention in the US, an analysis of the problem and an Immigration Detention Syllabus
Episcopal Migration Ministries

The Welcoming Services page gives a good overview of the types of services and aid needed from the beginning, and they provide an asylum toolkit
The UN Refugee Agency (UNHCR – United Nations High Commission for Refugees)

Flow Chart of Asylum Process and Help for Asylum Seekers