LongSpear is a Cocoa-based Dungeon Master's assistant. It is not intended as a means for storing all the information about your party in the long term, but rather to help with the tedium of rolling skill checks and keeping state in a given battle.
It does allow you to enter certain information that is retained between sessions, such as the names of the party and important skill bonuses. It contains a database of monster information imported from the Monsters Manual, and during battles it tracks initiative and turn information. It also can track spells and other effects, remembering their duration, as well as tracking which monsters were killed and which fled.
I find it pretty useful, you may too. It is written in Objective-C. Some screenshots are included below.
There are a few bugs and missing features, and so the current status is at beta. Unfortunately, the project has reached that dangerous point where I'm pretty happy with how well it works despite its flaws, so progress towards 1.0 may be slow depending on how busy I am. Unless of course you help me out!
To download, go to the SourceForge page. From there you can download any releases or check out the most recent version from CVS.