The Great Migration is an ongoing project of NEHGS. The first set of books covered immigrants to New England who appeared in records between 1620 and 1633. They are now working on those who appeared in 1634 and 1635. Each head of household is profiled, including migration, parents, records in the New World, marriage, children, family connections among immigrants, and explanations where necessary where there are more than one person of the same name. The spouses of children are given, but children are not separately profiled if they immigrated with their parents.
NEHGS members can search the published volumes (AmericanAncestors link). For an extra $10, you have access to profiles of those who have not yet been published. The general public can find information at GreatMigration.org on what profiles have been published, and information on purchasing the books.
The sketches are sourced using shorthand abbreviations. The Society has provided a key to more common abbreviations here, however that page is restricted to member-only access. An abbreviation can sometimes be decoded by using a search engine search for the abbreviation along with "Great Migration" or similar.
The next set of volumes by the project is The Great Migration: Immigrants to New England, 1634-1635 which was completed in seven volumes, published biennially from 1999 through 2011.