Building a collection: advice for newbies, DJs and collectors alike, by Michael Lavocah
Guide to Orchestras by Dan Boccia
Guides to Tango Music for Social Dancing, by Stephen and Susan Brown
Tangoplaylist.com by Anton Sukhanov
Tango music 101, a one-page basic intro, with starter album recommendations, and a 60-CD must- have list for beginning DJs, by Tine Herreman

The DJ's role, by Stephen Brown
DJs about DJing
Veronika's advice

Stephen Brown's Annotated List of Tandas

Sharna's DJ List of Neo Tangos 
neotango.info
Jackie Wong's neo picks
neotango.de
Veronika's resource
review of electrotango CDs

Todotango
Discographies at tangodj.org
Juan D'Arienzo discography by Johan
Astor Piazzolla discography
A beginners guide to tango record labels

Gracenote

Todotango
Totango

Gardel server (searchable)
Todotango

Tejastango Links

Zivals (tangostore.com) in Buenos Aires
El Bandoneon in Barcelona Spain
milonga.co.uk in United Kingdom
Tango Nada Mas in Chicago
ToTango in Montreal Canada
The Tango Catalogue in Massachusetts
Danza y Movimiento in Germany
Club de Tango in Buenos Aires (no credit cards)
Buenos Aires Tango Club in Buenos Aires (no credit cards)

Wikipedia comparison tables of Media Players (features, platforms, formats, etc)
mp3cut, freeware for recording, editing mp3s without decoding an re-encoding
Lame encoder v3.96.1 (freeware) 

Dan Boccia's recommendations for sound systems
Fender Passport

Tango DJ discussion forum  150+ DJs and collectors from all over the world. Collaborative, friendly. We're there for the information, not the opinions. Membership must be approved. DJ's/collectors only, beginners welcome.

eng.tango.info/deejays 
listing on Tangopulse

La 2x4 La Radio de Tango de Buenos Aires (by GobBsAs)
Radio Cubik Network
Todotango
Tunez - Tango Radio
Radio Buenos Aires, listen to neotango, go to this link and look up Radio Buenos Aires
neotango.de

Tango styles table
DJs about DJing