Slidehare www.slideshare.com has been around for a while. Basically, it's a "youtube for powerpoint presentations."
Recently slideshare announced pricing for its premium offerings. http://tcrn.ch/cmit6n
The basic account is free and has powerful SEO (search engine optimization benefits.
Most orgs have a stash of presentations languishing on their employee's hard drives. If you take these powerpoints and post them to slideshare with titles filled with keywords and those presentations will show up very high in google search results.
