Prezi -- I'm happy to learn that there is a more dynamic alternative to PowerPoint. I think I only ever worked with PowerPoint one time when a little 4-Her came into the library needing to make a PowerPoint presentation for the fair. Talk about the blind leading the blind -- but between her, her mother and me we got 'er done.
I've always thought PowerPoint presentations were boring, boring, boring. Prezi allows a presenter to put on a much better show. After watching the demonstration videos on how to do a Prezi I think it would take me quite a while to get my brain around the process. However, since I don't do presentations it's unlikely I'll ever do much with either Prezi or PowerPoint.
Two other services mentioned in the Prezi page were ZamZou for free online photo format conversion and Picnik for online photo editing. I played a little with both of them and they are pretty slick.
Slideshare This would be a great service for someone doing lots of different presentations, especially if one traveled a lot doing so. It's a service that hosts your presentations all in one place where they will be available on any computer with online access. How great would that be if you arrived at your destination and found that the file on your computer was corrupted? It also makes your presentations available for others to find and share. Can it be used for Prezis? I didn't see anywhere that it said if it could or not.
Prezi, Picnik and SlideShare all have limited free versions. If you want a little more they all cost money. Prezi - $59 yr., Picnik - $2.08 mo., SlideShare - $0 - $249 mo. with special pricing for non-profits. I think I'm seeing a trend here -- the programs we use being "in the cloud" and us needing to keep paying a monthly or yearly fee to use them. When will all this become too expensive for the average working person to afford? Think about it -- every program you need to use to do word processing, bookkeeping, play music or videos, edit & store pictures, manage your family tree -- all in the "cloud" and demanding monthly or yearly fees to use & have access to your material. I don't think I want to go there.