Since 138's topic has grown and Stage links are scattered in between pages, here's an updated one post list of all Stages posted here so far.
Starting with SoundClick and GarageBand Accounts. These accounts are free to make. And easy to upload to. They contain all Stages that the user has uploaded to it. So, expect each SoundClick and GarageBand Account to have oodles of Stages and Replays. To see more of the Stages and Replays not displayed on their SoundClick home page, click on the blue link on that says "music page".EskimoMario550's SoundClick Account - http://www.soundclick.com/bands/default.cfm?bandID=864890
138hpl's SoundClick Account - http://www.soundclick.com/bands/default.cfm?bandID=864622
retypepassword's SoundClick Account - http://www.soundclick.com/bands/default.cfm?bandID=864959
kchant's SoundClick Account - http://www.soundclick.com/bands/default.cfm?bandID=869160
blacksnake16's SoundClick Account - http://www.soundclick.com/bands/default.cfm?bandID=865030
HugeRobot's GarageBand Account - http://www.garageband.com/artist/michaelgrubb
Here is a list of those who host Stages on Youtube. Another fine idea.Mokona7's Youtube Account - http://www.youtube.com/user/mokona7
EskimoMario550's Youtube Account - http://www.youtube.com/user/insano41
Next up, individual Stages. Single Stages and Replays by GFaqs users. Because some people are just to darn lazy to make a SoundClick or GarageBand Account. >__>SixFortyFive's Stages:
http://www.sixfortyfive.com/temp/bangaio/stages/Boss%20RUSH!.mp3
http://www.sixfortyfive.com/temp/bangaio/stages/Boss%20RUSH!%20(Replay).mp3
Wired79's Stages:
http://rapidshare.com/files/141445242/Bangai-O.rar.html (A pack containing tons of Stages)
Xion350's Stages:
http://www.geocities.com/xion350/BossRush.wav
Brawl Code: 5112-3076-5657
I plays a meeeean Lucas. My second and third are Weegee and Oldmanondorf.