From the Working Class Studies Listserv (with a few additions):
AFL-CIO*
https://secure.ga3.org/08/UCF_Katrina_Relief
Air Line Pilots Association
http://crewroom.alpa.org/DesktopModules/ALPA_Documents/ALPA_DocumentsView.aspx?itemid=1847&ModuleId=803
Amalgamated Transit Union
http://www.atu.org/docs/about_atu/about_announcements.html
American Federation of Teachers
http://www.aft.org/news/2005/katrina/whatcando.htm
Bakery, Confectionery, Tobacco Workers and Grain Millers International
Union
http://www.bctgm.org/Special/FH_IDRF%20letter05.htm
Communications Workers of America*
https://secure.ga3.org/08/cwa_katrina_relief
International Alliance of Theatrical Stage Employes, Moving Picture
Technicians, Artists and Allied Crafts
http://www.iatse-intl.org/news/pr_090105.html
International Association of Bridge, Structural, Ornamental and
Reinforcing Iron Workers
http://www.ironworkers.org/news/news_details.php?news_id=243
International Association of Fire Fighters*
http://daily.iaff.org/083105KAdd.htm
International Brotherhood of Boilermakers, Iron Ship Builders,
Blacksmiths, Forgers and Helpers
http://www.boilermakers.org/hurricane.htm
International Brotherhood of Teamsters
http://www.teamster.org/05news/hn_050830_2.htm
International Longshoremen’s Association
http://www.ilaunion.org/LetterFromJohnBowersKatrina.PDF
International Union of Operating Engineers
http://www.iuoe.org/cm/training_site/relieffund.html
International Union of Painters and Allied Trades
http://www.iupat.org/news/relief.html
Laborers’ International Union of North America*
http://www.acteva.com/booking.cfm?bevaid=94825
National Air Traffic Controllers Association*
http://www.natca.org/mediacenter/hurricanekatrina.msp
National Education Association
http://www.nea.org/presscenter/katrinahelp.html
Seafarers’ International Union
http://www.seafarers.org/HeardAtHQ/2005/Q3/sdrf.xml
Service Employees International Union*
https://secure.ga3.org/08/katrina
Sheet Metal Workers International Association
http://www.smwia.org/news/index.cfm?fa=viewArticle&id=231
UNITE HERE
http://www.unitehere.org/hurricanerelief.asp
United Steelworkers
http://www.uswa.org/uswa/program/adminlinks/docs//Katrina%20Letter%20-%20United%20States.pdf
*Accepts immediate online donations.