Reunion is a popular, long-lived, Mac-only genealogy program that can help you organize, view, and show off your family tree. Of the many genealogy options out there, Reunion tends toward the higher end, but it comes with many extras--and boasts a long, stable track record--to justify its price.
This app comes with much of the functionality you might expect, making it easy to quickly add family members (with predictive text), fill out notes and various data fields, cite source documentation, quickly perform searches, import data from other programs (essentially, from any app that uses GEDCOM files), and even run customized lists and reports. Where Reunion really shines is in its cool extras, like support for a variety of media (including pictures, movies, and audio), quick calculators for dates and relationships, slick output options for Web pages and even iPods, and integration with a new iPhone app. Reunion is also designed with family reunions in mind, helping you set event reminders, create mail-merge files, and generate large, attractive family trees for printing.