Haiku Deck is a free, user-friendly website and iPad application that creates presentations quickly! Haiku Deck's templates make presentations easy and exciting. Have students create them on their iPads and then access then from a PC.
Slideshare is a site where you can host your presentations and share them with others. Presentations can be linked to at the site itself or else embedded in a web page. You can also synchronise an MP3 audio file (podcast) with the slideset to create a slidecast - a more powerful way of distributing presentations/tutorials. Slideshare is also a tremendous resource site of presentations