Simply go to the person's briefcase. If, for example, his Yahoo! ID is Yahoo_JoeUser, you would go to http://ca.briefcase.yahoo.com/bc/Yahoo_JoeUser.

You can then download and view the files in that person's folder. (Note: Only access files from people you trust.)

You can now also easily access someone's briefcase by looking at their public profile. If that person has chosen to list their briefcase on their profile, all you need to do is click on the link to access the public files in their briefcase.