I build a handy little tool for converting files into data URIs this weekend:
I posted a walk through of the code to the Bocoup Weblog.
There is some argument about the terminology here. The actual browser
FileReader host API method for doing this is called
readAsDataURL, but it's not really a universal resource "locator". It's more of an "indicator" describing the data inline. More importantly, "dataurl.com" was taken.