Dropbox is a popular website for storing files online. You can create an account for free.
You can automatically include links to files (docs, pdfs, photos, music, etc) in your dropbox on the Event Editor.
First, click the dropbox icon on the Description field toolbar
Next, sign into your dropbox account if requested:
Finally, browse to the file you want to attach, and select it:
That's it! A link to your file will be included, along with a small icon: