One of the nice elements of PPT 2007 ribbon is the way it previews master slide options. Here is a recent presentation with 4 master slides:

This really shows the slates mentioned in the previous post. For this presentation I only have one background for the speaker content (#1 – Purple) and 3 slates. Of note: I color code the speaker slates so I know what type of information it contains before reading it (especially when viewing slides in slide sorter view). Here the breakdown of each:
1. Content background and the 5 layout options developed for it
2. Video slate: hidden slide that tells me what video is to run at that point of the presentation
3. Speaker slate: hidden slide that tells me which speaker will be on stage (this presentation has numerous presenters)
4. Misc. slate: hidden slide that is used to tell me everything else, from web demo to break

– Troy @ TLC