I know they've been around forever, but recently I've discovered the wonderful world of mash-ups. I'd heard of remixes, medleys, and samples, but I had never really come across the strict genre/world of mash-ups.
For those who don't know what a mash-up is, it's basically the combination of various tracks from various pieces of music all placed together to create a new song. Sometimes additional audio elements are thrown in to make the track more seamless, such as additional percussion or synth tracks. An example would be taking beats from Daft Punk's "Da Funk" and adding in the vocals from Queen's "Another One Bites the Dust" (making "Another One Bites Da Funk"). If you're still a bit fuzzy here is an excellent video giving a brief demonstration.
After scanning some mash-ups I've found some can be playful and fun, others transcendental, and even more just plain awful. Some of my favorite mash-up artists include Party Ben, Norwegian Recycling, and DJ Earworm. And a great catch all source is a neat little website called "Mash-up Town".
Overall I love the concept. I love finding music that opens up my mind, and I've found this subculture has definitely done that. And plus who doesn't love hybrid song titles like "Drop It Like It's a Whole Lotta Love", "Shut Up, American Boy", and Sweet Mama O'Mine". Check out and support your local mash-up artists, you'll hear music in a whole new way, I promise.