These are AMV or Anime Music Videos, made by fans splicing video clips with music. And yes, it's legal - US Copyright Office said so. If you don't watch a lot of anime, some of these will not make sense. In which case, just listen to the music. But if you have questions, ask. Sad mix.
* Fireflies * Anime Mix amv by Pozorrogo
Metropolis - Eiffel 65/Silicon Girl + Evanescence/Wake Me Up Inside
FLCL - Gary Jules/Mad World
AMV - Iriya no sora UFO no natsu, song - She will be loved
Kenna - War In Me (Haibane Renmei - Charcoal Feather Federation)
Cowboy Bebop - Seatbelts/Call me Call me