Alsace (Ger. Elsass) is now two French departéments, Bas-Rhin  (Lower Rhine) & Haut-Rhin  (Upper Rhine). The Territory of Belfort  is sometimes also included. The Territory of Belfort was formerly part of Haut-Rhin. From 1789 (French Revolution) to 1871, the Departément of the Territory of Belfort didn't exist, because it was included in the department of Haut-Rhin. After the war in 1870-1871, all of Alsace was annexed by Germany except the region of Belfort, which became the "Territory of Belfort" (departément n° 90) in France. After World War I (1918), Alsace became part of France, but the Territory of Belfort remained a separate departément. So, if you have an ancestor who lived 1789-1871 in Haut-Rhin, check for records in the Territory of Belfort. In general, the Alsace was French 1648-1871, German 1871-1918, French 1918-1940, German 1940-1945, French since 1945.
A short timeline-table, called Alsace-Lorraine — an Enclave of Ethnic Germans in France: http://dgmweb.net/genealogy/Ancillary/Geog/Europe/Alsace-Lorraine.shtml
Archives départementales Alsace
Alsachat.net - come chat with us!: http://alsachat.net or irc://irc.rootsweb.com/alsace
Maps of the Alsace: http://freepages.genealogy.rootsweb.com/~valorie/alsace/maps/
The Alsace-Lorraine list: http://freepages.genealogy.rootsweb.com/~valorie/Alsace-Lorraine-L.htm
More Alsace lists: http://genweblog.blogspot.com/2006/02/alsace-genealogy-lists.html
Alsace Message Board: http://boards.ancestry.com/mbexec/board/rw/localities.weurope.france.alsace
Alsace & Emigration Links (CoolLinks): http://sdrescher.net/php/linkdex/index.php
The Süss Collection: http://valoriez.blogspot.com/2004/08/sss-collection.html
Alsace Topliste: http://alsachat.net/top
Stammtisch Alsace - Topliste Alsace Genealogy Forum: http://sdrescher.net/phpBB2/
You can use some of the general sites where you can search for surname distribution to pin down villages /communes for further study, if you are researching a relatively rare surname. Some of these sites for France are Notrefamille (1890), GeoPatronyme (1891-1915, 1916-1940, 1941-1965, & 1966-1990), and GeneaNet (European GEDCOMS). The French Telephone Directories: http://www.pagesjaunes.fr/trouverunnom/RecherchePagesBlanches.do or http://www.infobel.com/france will do the same thing for surnames existing today. For more on surnames, see: http://genweblog.blogspot.com/2006/03/surnames.html
How to use the Le Centre Départemental d'Histoire des Familles (CDHF) website: http://valoriez.blogspot.com/2005/01/le-centre-dpartemental-dhistoire-des.html
Historical Maps of the Alsace (l'Atelier de Cartographie du Département d'histoire de l'Université de Haute, Alsace): http://www.cartographie.histoire.uha.fr/
Modern maps: http://www.cg68.fr/PGconteneurs18.asp
If you know the village name, but not where it is located, try Locom.org - Bas-Rhin, Haut-Rhin, Territoire de Belfort. This site also works for the communes of Lorraine.
Alsace History Timeline: http://dgmweb.net/genealogy/Ancillary/Geog/Europe/Alsace-Lorraine.shtml
1836 Census Surname list - Strasbourg (10,846 names): http://www.census1836.com > List of Surnames.
District of Wissembourg (6,750 names) & Bischwiller & Haguenau (47,843 names) are now also available.
Robert Behra has found an "Index of 2090 marriages (1694-1796), 290 baptisms (1694-1834) and 110 deaths (1694-1824) recorded in the registers of the Catholic parish of Our Lady of Mariastein, in Canton Solothurn, Switzerland, quite close to the border with southern Alsace. Mariastein was a well known place of Marian pilgrimage in this region, and an especially popular place to get married in the years 1792-1798, due to the French Revolution. About a third of the marriages in this index involved someone from southern Alsace. You can read a bit about Mariastein in English at http://www.kloster-mariastein.ch/us/ (French and German also available). The original records from which this index was made are available on FHL microfilm no. 1632852. The index was done by Suzanne Allemann in 1991 as cahier 14 of ALEXSYS, the program for publishing systematic abstracts of marriage and other records organized by the Cercle Généalogique d'Alsace."
Communes of the Bas-Rhin département: http://en.wikipedia.org/wiki/Communes_of_the_Bas-Rhin_d%E9partement
Communes of the Haut-Rhin département: http://en.wikipedia.org/wiki/Communes_of_the_Haut-Rhin_d%E9partement
New home for The Communities of Alsace A-Z: http://www.rootsweb.com/~fraalsac/alsaceaz
Jewish Alsace Community (in French): http://www.sdv.fr/judaisme/; Cercle de Généalogie Juive: http://www.genealoj.org/
Communes in France: http://www.answers.com/topic/commune-in-france
$$$ Old French Postcards: http://boutique.geneanet.org/catalog/cartes.php
Alsace GenWeb (in English): http://alsacegenweb.online.fr/homepage.htm
France Apprill & Serge Busiau's AlsaceGénéa: http://www.alsacegenea.org/ - in French, but buttons for Reverso translations
Some extracted parish records - Bas Rhin : http://www.caids.net/cgi-bin/depouill/search_depouill.pl
Haut Rhin : http://www.caids.net/cgi-bin/depouill/search_depouill.pl
More départements: http://www.geneactes.org/index-en.html
Up until 1871, the Territoire de Belfort, which today is part of the region known as Franche-Comté was in what today is the département du Haut-Rhin. The Lisa90 site:
http://www.lisa90.org was put together by volunteers who are
systematically abstracting the church and civil records for the 101 communities in Belfort.
My Alsatians, the Baysingers of Alsace: http://freepages.genealogy.rootsweb.com/~valorie/alsace/
If you find the ship your immigrants took, and they departed from Le Havre, write to "Archives D'partementales de la Seine Maritime, Cours Clemenceau, 76036 Rouen Cedex, France" to request a copy of the passenger list of that particular ship. Of course, there are no guarantees that the passenger list exists.
French Emigration Indexes: http://valoriez.blogspot.com/2004/07/french-emigration-indexes.html
Travels in Alsace & Lorraine Articles Online: http://valoriez.blogspot.com/2004/08/travels-in-alsace-lorraine-articles.html
Hint for using the FHL Catalog when there are LOTS of categories: http://archiver.rootsweb.com/th/read/ALSACE-LORRAINE/2004-01/1073853693
When you have exhausted the holdings of the LDS, read Robert Behra's post about Village Records. Another post about Military conscription records, shows you how to find the records, and use them to find a family at a particular time, in a particular place. More French military indexes - SGA - mémoire des hommes: http://www.memoiredeshommes.sga.defense.gouv.fr/index_en.htm
Bas Rhin soldiers of the Revolutionary Army, First Empire (Napoleon): http://membres.lycos.fr/mylak/militair.html - in French
Some Late Nineteenth Century Alsatian Folk Dress: http://www.siue.edu/COSTUMES/COSTUME16_INDEX.HTML#Plate95
L'Alsace Spécifique (English page): http://mapage.noos.fr/ephil/uk_alsa1.htm
Wonderful discussion of the geography, history, language and culture of the Alsace, by Eugéne Philipps.
Simultaneum in the Churches of the Alsace: http://genweblog.blogspot.com/2006/05/simultaneum-in-churches-of-alsace.html
Interesting discussion of The Linguistic Tug-of-War between the French and German languages in the Alsace, based in history and linguistic analysis: http://thesis.haverford.edu/archive/00000114/01/2003KegelT_linguistics.pdf
If you think your Alsatians may have come from Switzerland after the 30 Years War, and you have a relatively uncommon surname, check the microfiche Switzerland-Surnames at your local FHC, number 6053507. It will list the cantons where the surname can be found in Swiss records. Thanks to Margaret Miesterfeld on the Alsace-Lorraine list for this tip.
French History Timeline: http://www.uncg.edu/rom/courses/dafein/civ/timeline.htm
Huguenot Research: http://valoriez.blogspot.com/2005/01/huguenot-research.html
Naming customs in Germany and France: http://valoriez.blogspot.com/2004/02/naming-customs-in-germany-and-france.html
Lorraine links: http://genweblog.blogspot.com/2006/04/lorraine.html
Book on French social history: The Ancien Régime, French Society, 1600-1750, by Pierre Gourbet, 1969. English translation Steve Cox, 1973, Harper Torchbooks, Harper & Row, Publishers, Inc., First Harper Torchbook Edition 1974. ISBN 0061318221.
The ability to simplify means to eliminate the unnecessary so that the necessary may speak. - Hans Hofmann