As an aside to Eric's format request I wanted to point out another small issue students have had with web attachments.  There are several ways to attach files to a blog entry, the two main ones being "Attach audio files" and "File attachments" (see below).  The former is for audio formats such as wav or mp3 (these will show up with a little play button).  The latter is for everything else, anything you want to see listed at the bottom of your message as a downloadable file (.rns, .doc, .pdf, etc)...in other words just like email.

This image shows how they appear when you are creating a new entry: