Though I am a fan of Apple—I am writing this article on my MacBook Pro—my slideware of choice is actually Microsoft PowerPoint.
I do have Apple's Keynote, but I have never come across a compelling reason to use Keynote instead of PowerPoint.
However, using PowerPoint isn't always an option. Even if it is, sometimes you don't want to use the same old slides, or you may need to collaborate with a dispersed team online and sending files back and forth doesn't cut it.
Here are a few alternatives to PowerPoint, both online and off. Neither the list nor the descriptions are extensive, but hopefully they'll get you started in the right direction.
It has the same functionality as PowerPoint, but it was created by a company that actually wants to make things easier for their users. If you've got a Mac, Keynote may be a great choice. You can even save your Keynote presentation as a PowerPoint file, so you don't have to worry about compatibility.
Prezi takes presentation design off rigid, stand-alone slides and creates a presentation in its own environment. Prezi considers itself the "zooming presentation editor." It's a pretty cool application and has been used successfully during TED presentations, but I've rarely seen it used well anywhere else. It can be used as a collaborative online tool, or locally.
SlideRocket is online presentation software that takes the basics of PowerPoint presentation design and puts them in an online environment that enables team collaboration and easy access, including mobile. There is a free version that includes an Inspiration Gallery, complete with a template designed by yours truly.
4. The spoken word
My presentation colleague Adam St. John Lawrence would kill me if I didn't put this in here. Of course, you don't always need slideware.
If you have a compelling story and fear that you can't design an effective presentation, consider other routes. It can be as simple as pulling up a stool and talking with your audience, or as intricate as rehearsed skits, improv, props or live music.
These are the big three (or four) of presentation platforms, but there are some other smaller players as well. If you run into the issue where you have designed slides but can't use PowerPoint, consider saving them as a PDF and presenting them that way (albeit without animation or video) or post them to SlideShare.
Jon Thomas is the founder of Presentation Advisors, and the Director of Communications at Story Worldwide. He blogs at PresentationAdvisors.com, where a version of this article originally ran.