SlideShare lets you share your slides, and how I've wanted something like this. I've tried out a few other share presentation sites, but this is by far and away the easiest. Upload your .ppt/.pps or .odp presentations, wait a few minutes and bingo.. it's there waiting to be used, either in the browser window or there is an option to use it full screen.
It can be a little slow to move from slide to slide, particularly if the slide is graphics heavy, but once it's sorted it the once it's pretty much fine from then on.
As you'd expect with a 2.0 application you can add comments to the slide show, tag it, describe it and search for slide shows. The search function wasn't great and retrieved 0 results for Web 2.0 and variants until I tried web2 at which point it came back with 60 results.
Slideshare IS open space, so it's not suitable for any private/confidential material.
You can embed slides, or just provide the link, either to a presentation itself, or to an individual's collection. I have to say that I really like the look of this, and I'm going to be adding a lot of my presentations up onto this system - not always necessarily to use, but to keep in one place.