SplashCast
SplashCastMedia offers their SplashCast video slideshow device, which is quite possibly one of the most interesting and robust available. Each slide can be a document, image or video. You can search for and selectively include images from Flickr and videos from YouTube, or upload your own. You can compose text documents in their SplashCast console. The alternative to a customized show is to specify either a Flickr or YouTube RSS feed. You don’t have control over the items, however, a new release is coming, with many more feed-based features. You can see examples at 901am.
Slide
Slide has standard web slideshow features, allowing you to build a presentation with a sequence of images you choose. You have a several viewer options in terms of size, shape, skin, and type of transition. Where Slide differs from most similar packages is that you can give it the URL of any RSS feed where each item contains an image and produce a slideshow out of those pics. That means you can use custom feeds from, say, Yahoo Pipes or other Web 2.0 mashup tools.
ThinkFree
ThinkFree has a viewer plugin for the WordPress blogging platform which supports various Microsoft Office files (documents, spreadsheets, presentations). Clicking on an appropriate link brings up the display of the file in question.
To incorporate ThinkFree in other web applications, there is a viewer API. [via Mashable] The plugin itself supports ThinkFree files, which are compatible with the above-mentioned Office files.
The only drawback I see from using this plugin is that your “office” content may not get indexed by search engines. Although I haven’t tested it yet, so I may be wrong. On the other hand, if you upload Office files to your web server and link to them from your blog posts, those files will definitely get index by most of the major search engines.