I'm surprised nobody listed this one yet... it's fairly old school at this point, but still fairly awesome. This is the first vid that I had to classify as epileptic, and also probably the first that every made me want to get up and dance.
<b>Video:</b> <a href="http://www.animemusicvideos.org/members/members_videoinfo.php?v=23350">Delirium</a>
<b>Category:</b> Action, Fun, Dance, Other
<b>Anime:</b> Card Captor Sakura, Full Metal Panic, RahXephon, +40
<b>Song:</b> Children in the Sandstorm
<b>Artist:</b> Robert Miles & Darude
<b>Creator:</b> <a href="http://www.animemusicvideos.org/members/members_myprofile.php?user_id=69640">Anamorphic Productions</a>
Also, while I'm not sure I'd classify it as a <i>dance</i> video per se, it's definitely upbeat. What would happen if Edward Wong Hau Pepelu Tivrusky IV decided to send dance music to everyone in AnimeWorld? This, apparently. It's a video full of good times and happy, and makes the second best use of both the Haruhi Dance and the Lucky Star Dance that I have ever seen (the very best being the already listed Feel the Mambo by ScorpionP).
<b>Video:</b> <a href="http://www.animemusicvideos.org/members/members_videoinfo.php?v=155593">Do the Diggy Dumm</a>
<b>Category:</b> Comedy, dance, fun
<b>Anime :</b> Azumanga Daioh, Cowboy Bebop, FLCL (Fooly Cooly), Lucky Star, Melancholy of Haruhi Suzumiya
<b>Song:</b> Dumm Diggy Dumm
<b>Creator:</b> <a href="http://www.animemusicvideos.org/members/members_myprofile.php?user_id=713842">DoomDragon6</a>