I haven't discovered a new song, but a whole genre. Industrial.
I love Metal, Power Metal, Heavy Metal, Nu Metal, Rap/Rock, Symphonic Metal, and my knowledge of genres pretty much dies there. There's so many different varieties of 'Metal' and I only know the ones I listen to long enough to pick up the word (and likely misuse it).
Now, through Nightcore remixes, I've found Dubstep, which at first I hated (because the popular stuff wasn't very good) but found some really great stuff, like Celldweller and Blue Stahli, and listening to them lead me to a lot of Youtube videos about 'Dark Industrial Electro' or 'Cruelstep' or 'Metalstep Mix'.
I really don't know of any Industrial bands though, I only have the hour long mixes I find.http://www.youtube.com/watch?v=cNAdtkSjSps#wshttp://www.youtube.com/watch?v=EFL1-fL-WtM#