Web/iPhone/Android: Got a PowerPoint presentation you want to share with co-workers or clients on short notice, or who are in a different timezone? Free tool MightyMeeting lets you conduct presentations remotely via the web or its iPhone and Android applications.
Upload any PowerPoint presentation or PDF to the site to get started (or just forward presentations from your email account to a private email address) to get started. Once your presentation is in the cloud, you can invite anyone to join you. When they click through to your presentation, they're looking at the presentation as controlled by you — again, either from a web browser of your iPhone or Android device.
As I mentioned, the free web app could come in particularly handy for short-notice presentations — you don't have to set up any projectors or have any files on hand. All you need is a supported device on your end and a laptop the people you're presenting to can look at. (You can invite multiple guests, too, so a room full of people could watch your presentation directly in front of them.)