If you need to easily display slideshows online, there are a couple of options that I have recently run across. The simplest, though not as sophisticated, process is to use a site called Flickr, which was recently acquired by Yahoo! and can be a lot of fun. You just upload your pictures and folks can link to them to form online picture-sharing communities. The best feature is that it can export to your blog or website, though the format is not as customizable as I'd like.
This type of slideshow would be good for nonprofits that need a way to showcase their activities on the web. There are other, more expensive solutions, but they are often overdesigned (with noises and animations at every click of the mouse).