PowerPoint 2010 includes a 'Package Presentation for CD' feature which claims that it will include the "Microsoft PowerPoint Viewer to play this presentation". But all it actually does is embed a link allowing you to download the viewer on the target machine, which doesn't seem especially helpful.
Tech writer Helen Bradley points out the inconvenience on her blog, noting that the language Microsoft uses to describe what gets saved on CD is downright deceptive and is likely to catch some users out:
Many hapless folk are going to assume that it all works as it has in the past and arrive at presentation time without PowerPoint on the computer they are presenting on and having to download and install the viewer before they can begin. The situation will be worse still if an internet connection isn’t available.
Why Microsoft couldn't simply bundle the viewer, which it freely allows anyone to download, is an interesting question. The bottom line? Don't assume the viewer will be around, and keep a ready-to-install copy on USB if you make a lot of presentations.