What is AMV? To make it easy for me I could say visit www.animemusicvideos.org and all your questions (even those you didn't dare to ask) will be answered.
But in brief : with an AMV you try to make a musicvideo (like MTV). You use a already existing song and arrange videosequences to it that you take from one or many ( maybe hundreds) animes. You add digital effects, text, pics ... and mix it all together in a way your creativity and computer power allows it. Beeing a musicvideo usually the music leads the way and the videosequences are arranged accordingly. Often that is exactly what happens. But there is also the contrary philosophy that the music is choosen to the specific mood or story of the anime and therefore the result is more like a soundtrack to a retold or newtold story. That especially happens with AMV that are based on a single anime (like mine does). There are some interesting Noir-AMV out there, e.g. one called Deja-vu, that tells the story of ep.6 "Black thread of fate" in a new way of "what if" : what if Mireille dropped Kirika and tried her escape alone. Scenes from the episode are cut together, sometimes digitally blended, to tell the story a different way. A very creative and interesting video. Thats about in short about AMV in general.

technical details :

Although I wanted to avoid proprietary code or plugins on this site, I have made a inline-preview of the videos via the flash-format. Now there is a small player window left to the bigger pictures (using the Flash Player), which is capable of displaying files in the flv-format (the player is just 3kb tiny,so it is loaded nearly instantly, but of course, the files themselves are about 1-2MB big, so it may take some time to load).
Because not installed, or not correctly working plug-ins can lead to a lot of hassle, up to a total "hang" of the browser, I put the flash videos into I-frames, that are only loaded after a click on the respective link. If that link leads to any kind of trouble, just use the ordinary download links instead, when you visit next time.
Newly added (at end of 2007) is a little web 2.0 feeling. You can change the size of the pictures and video-boxes via the two according sliders. The buttonsYM stand for Your resp. My comments and are responsible for blending in and out the according areas. This is achieved by the use of the libraries Prototype and Sriptaculous.
To all non-windows, non-IE, Opera or FF Users : I have no idea what will work for you and what not. Sorry for every trouble this site causes you. Suggestions or errors can be mailed to me or posted on the comments page.

Picturesize Videosize Your Comments My Comments
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Just a short hint for two AMV that are for different reasons two of the best AMV I ever saw :