I guess it depends on what you call Modern. An almost brand new song, unquestionably a tango, is Leandra Gamine's debut single "Tango," and very dance-able. If you want something 'fast,' try "Objection" by Shakira. "Dance with Me" by Debelah Morgan is a pop version of Hernando's Hideway from maybe 8 years ago. "Running Scared" by Roy Orbison is another unquestionable tango pop song (I say that because so few pop songs seem to have both the beat and flavor of tango - and these songs have both), but hies back to 1961. If you do American style, the title track to the "Phantom of the Opera" soundtrack is a good tango too, though not exactly exactly what I'd call pop. "Tango in the Night" by Fleetwood Mac is a tango, but the beat seems a little soft for some. "Indian Reservation," another 60's song by Paul Revere and the Raiders, has the S-S-Q-Q-S beat of American tango, but lacks a little bit of the proper feel.
If anybody else knows some good "pop" tangos, I'd be interested!