Features I like in: Powerpoint 2007
This is the 2nd in my series of useful features in products we all use. This may be a well known one but I only started using it recently and have found it incredibly useful.
Delivering a presentation on 2 monitors (or more likely on a projector)
I deliver a lot of presentations in my work as a technology evangelist and powerpoint is something I use on a daily basis. With this feature, you can view the slide, see the presentation notes, keep tabs on the time and highlight points on the slide on your monitor while the audience sees only the final version of the slide in their view. See the article linked above for a detailed explanation but you'll find the feature in "Slide Show-> Use Presenter View and Show Presentation On:".
Not sure how many of you do presentations that regularly, but it's been a great thing for me.