I'll be gradually adding sources for tango music and dance.

• Todotango.com
  This is a great place to listen to or read about Argentine tango music. I'm pointing you to Canaro, but there are many other musicians here. It IS a bit slow to load.
  
  
• Free-scores.com
  You can search by style:Tango and then narrow it down by choosing Instrument or Instrumentation. Listen or download mp3s (some midis) and sheet music in Acrobat (pdf) or Word (doc) format.