I've run a music blog for the past 8 years and I've used a ton of different discovery methods. In the earlier years blogs provided me with most of my content. As of the past year Soundcloud has really shown me a whole new world of music. When you play a single track it goes straight to a recommended track, generally right in the same vein as the previous track. I've found hundreds of great tracks I would have otherwise never known existed.

On an unrelated but interesting note: I'm still trying to figure out their recommended algorithm, it seems to be a mix of tags, and cross-referencing your account with who's liked/played a song. What I don't understand is if I listen to a folk song, it will generally play another completely unrelated folk song but with no folk identifiers (tags). I've concluded it's magic.