As a fan of his EntourageABMenu utility, I was pleased to discover that developer Jon Nathan has a new item in his kit: Dialectic, a phone dialing tool that has more tricks than a magician's convention. Dialectic replaces the older Jon's Phone Tool and provides a bridge between almost any Mac PIM or database (including Address Book, Entourage, Now Contact, Daylite and more) and phone dialing via VoIP systems, hardware dialers, modems, Skype and other voice chat apps, Bluetooth-enabled cellphones... the list goes on.
Dialectic can trigger events via AppleScript when a call starts, so pausing your iTunes playback (or indicating a call start in your billing tool) is straightforward. If you make a lot of phone calls, you might be interested.
The online help includes a crowded page of resources, apps and scripts to get you rolling. Dialectic is a Universal Binary, costs $25 for new users and requires Mac OS X 10.4 or higher.