Top 20 U.S. States with Highest Proportions of Lutherans in the Population (self-identification), 1990
Figures represent results of the National Survey of Religious Identification, phone survey a nationwide sample of 113,000 respondents, conducted by the City University of New York. Figures represent all people who cited "Lutheran" or a specific Lutheran denomination as their preferred religion, including people unaffiliated with any Lutheran congregation or denomination.
Source: Kosmin, Barry A. and Seymour P. Lachman. One Nation Under God: Religion in Contemporary American Society; Harmony Books: New York (1993), pg. 88-93.
Luther95 - "The New Online Home for Lutherans." Lots of great links, especially to individual churches.
Lutherans.Net - Huge amoung of resources, links, bible study tools, a discussion forum, etc.
Suite101 Guide: Lutheranism - Very high quality guide to Lutheran resources on the net. Run by a live (and obviously knowledgable) guide. Great place to go for an introduction to Lutheranism.