Some of my favorites
Hi Missa.
I think I am becoming a ballroom-dance-music-hoarder

. I'm always on the internet looking or asking DJs what they just played. Some of my American Tango favorites which weren't mentioned yet:
Modern (some electronica on the tracks):
-Asi Se Baila El Tango by Bailongo (The tango from Take the Lead with Antonio Banderas.) It's on Casa Musica The Best of Ballroom Music Part 13 (vol 28)
-Argentina Vieja from The Ultimate Ballroom Album 12 by WRD
-Tango Duett by Albana Di Re. Intense violin with electronic beat behind it. Available for download.
-Libertango by Bond. It's on Casa Musica The Best of Ballroom Part 14 but can be downloaded as an individual song from their Shine album and both versions are identical (down to a sort of whispered break in the middle)
-Eleanor Rigby by Daniel Garcia Quartet/Tangoloco. I think you can hear it on youtube but I had to order the CD (Tangos de Liverpool) from Argentina via ebay. Ticket to Ride on that CD is ok, especially if you're a Beatles fan, but significantly less dramatic.
-I've Seen That Face Before by Grace Jones. Downloadable. This is another version of Libertango, electronic and with lyrics in English and French.
-Libertango by Boulevard Tango Club. Downloadable. What can I say - I can't get enough of this song...
-Bust Your Windows by Jazmine Sullivan: the orchestrated version, not the dance-mix version. Wikipedia says this is the first hip-hop song with a tango beat. (I think this one _did_ get mentioned before.)
-Lenna Lepparkerttu by Katharina Kaali (in Finnish.) Downloadable.
-Gamulan by Trio Garufa. Repetitive and hypnotic, reminiscent of Gotan Project. Probably best for a social dance as opposed to performance.
Classical/Acoustic
-Joe Lovano Tango by Dave Brubeck. Jazz tango. Laid-back, and sexy. Available for download.
-Gitango by Helmut Lipsky (French film etc composer) from Moontide CD. It's sad and sweet and has a lot of variation. Not electronic. On itunes.
-A Day At The Races:Blue Venetian Tango by Cologne Radio Orchestra. Upbeat, from a (German?) film. MP3 on Amazon.
Also, Gotan Project has a new CD coming out in April. There's a clip of "La Gloria" on their myspace page which sounds like it could be an American Tango.

Their live version of "Santa Maria" from Gotan Project Live puts a slight twist on that song we all know so well, so that it sounds a little fresher.