Articles / General Information
Elizabeth Stewart Clark - A series of wonderful articles concerning Civil War Impressions and Dressmaking.
Dixie Outfitters: True History - Several small articles on a variety of information.
Conner Prairie - Several articles on living in the late 19th century.
The Ladies of Reenacting - The Victorian Era, some very nice information

Forums
Authentic Campaigner - EXTENSIVE forums, very active.

Diaries & Letters
Civil War Women - From the Special Collections Library of Duke University.
Civil War Women: Primary Sources on the Internet - Links to several diaries, and photograph collections from the National Archives.

Fashion Guidelines / Authenticity Standards
The Sewing Academy - Elizabeth Stewart Clark is who I consider to be the most knowledgeable person about Civil War Era clothing. This forum has extensive information.
Godey's Lady's Book Online - 5 issues of Godey's from 1850
116th Pennsylvania Volunteers - Civilian guidelines for a group in the Northwest, detailed with links to other sites for more information.
Fanny and Vera's Guide for Civil War Reenactors - This guide is very popular and is referenced on many websites. Detailed information.
In Timely Fashion - Very nicely written site from a young lady with many years re-enacting experience.
9th Pennsylvania Reserves - Civilian guidelines, nicely detailed.
Reproduction Fabrics - Period reproduction fabrics for your sewing projects.
Robin Stokes - Custom fashions, fabrics, yarns and fashion guidelines.
The Civil War Lady - What they wore from head to toe. Very nicely done.
The Gentlemen's Page - One of the ONLY sites I've seen dedicated to men's attire and manners. Some wonderful information!
Genteel Arts Academy - Conference and classes on creating reproduction garments.
Civil War Ladies League - Civil War etiquette for ladies and gentlemen
We Make History - Early Victorian fashion guidelines

Link Lists
14th Regiment New Jersey Volunteers - Very nice link list with military and civilian information.
Civil War and Related Links - Extensive link list, many subjects, some wonderful information.
Civil War Links - Very long list of links, not categorized, but some interesting stuff.
Battery B, 4th US Artillery - Some very nice links, clear at the bottom of the page.
Cyndi's List - Extensive link list, many categories, some great information.
Reenactors of the American Civil War - Great link list, many categories, some wonderful information.
Romance Reader at Heart - Links to all things Civil War.
The Civil War - Very large categorized link list with many topics.

Yahoo Groups
Citizens of the Civil War