Awaken is a very complete alarm clock and sleep aid for the Mac. One of its main features is the ability to play music for you at night and gradually decrease the volume to help you fall asleep and then wake you up at the time you specify in the morning, again, playing music. If you don't like waking up to music, and you'd rather hear sounds, there are a few available. And you can add your own. In addition to playing a song, playlist or sound, Awaken can also launch an application or automate task at the time your alarm is supposed to go off. This gives you a lot of freedom in customizing what your morning is going to be like in advance. You could open a web browser with all the pages that you visit each morning or video player with news.
Adding new alarms is very easy. You do it from the Alarm menu and then the "New Timer" button. A new window will pop-up asking you at what time you want the alarm to go off and which days of the week it should be enabled. Also, you have to select what type of alarm you want (sound, songs, etc).
The sleep timer allows you to play a song or playlist for a specified amount of time before the audio is stopped.
All in all, Awaken is a very complete app that is very customizable and totally easy to use. At $10, it is also very cheap.