Friends of mine were looking for a way of presenting their Powerpoint presentations on their new iPads. All the existing options want to create Pdfs or movies of the presentation. The problem with this is that you lose all of the animations, video and other features that you can produce on Powerpoint. SlideShark seems to have rectified this.
Released a couple of days ago it seems to have filled a need in the business community. The beauty of this is that loads of teachers also have existing PowerPoint slides - they now have access to these on their iPads. Get a copy while it is still free. This will be one app that hits the top 100 list very quickly and when it does it will cost you.