Is it possible to save http-hosted MP3 files directly onto an iPad? Is there a way to save an MP3 from a web server directly onto an iPad?  I can stream it through the browser, but there is no obvious "save" capability.  

Would it make a difference if the MP3 were an email attachment?
As fas as I know there is no way to save an MP3 file directly from the web. What you can do is jailbreak your iPad and then try saving it.