Fellow PPT MVP Echo Swinford has the most comprehensive list of new features (and a few now missing) at her site, echosvoice.com.
This is the most comprehensive compilation list I have seen with 60+ features listed. If you have been using PPT 2007 for a while, or recently moved it it, this has lots of good information on features you may be overlooking. Here is the link.
– Troy @ TLC