Mark,
Great list, thanks for posting!
By the way, please consider adding another cool Free site which I discovered recently called Box.net
The basic service is Free, and here's the rest of the plans:
http://www.box.net/pricingThe Free "Lite" account gives you 1 GB of web storage with max. file size of 25 MB per song or any other kind of file.
The great thing is that you can use their song player and set it for streaming, download or both, then link to your songs from your own website or when posting on forums for feedback, etc.
You can see access (stream or download) stats and offer related files such as Sheet Music (in PDF or MUS format) or even things like Midi files, since they support many kinds of file types including videos.
You can set things like private vs. public access to your content. In other words, it's not just a good place for general backup storage, but great for managing your music and promotional content in a kind of "cloud" environement which works well with any kind of website or community forums like we have here.
By the way... it appears that garageband.com will be shutting down on July 15th. Here's where I first heard about it:
http://www.hypebot.com/hypebot/2010/06/10-years-later-garagebandcom-closes.htmlMichael