Google Docs offers an undocumented feature that lets you embed PDF files and PowerPoint presentations in a web page. The files don't have to be uploaded to Google Docs, but they need to be available online.
Via Mark Wagners blog, Educational Technology and Life I was directed to the wiki he created for his recent Picasa in Education training session. The wiki itself is very sparce at the moment, but it does link to a PDF handout which provides a list of way
Learning does not occur spontaneously among a group of students, whether the setting is face to face or online. Online discussion requires structure just as in a faceto-face setting.