Ken Bereskin, product manager for Mac OS X, is running a series on new OS X features in Jaguar.
The first one some days ago was about the new calculator.
Slightly related, Brent is updating NetNewsWire every few days it seems like. It just gets better and better. :-) NetNewsWire is a RSS aggregator for Mac OS X. It's great. It will change the way you read the web(logs).