You can use PowerPoint, of course, but what else is there?  And why would you want to use it?

Online Slideshow Tools

• Google Presentations
• Zoho Show 

• 280 Slides
• Slideshare
• Slide

Something Else

• Animoto

• Voicethread

• Jing

• Xtranormal

• Ustream

• Prezi

• Museum Box

• Flowgram