Pages allows you to create documents, stories, and more. When you finish, you can even export your file as a PDF or other format as needed.
iMovie is a great resource for creating videos and allows you to add music and edit clips to make exactly what you want.
Keynote is the Mac equivalent of powerpoint. It is so simple to use, and can help you to make a presentation or to edit a picture using various tools.
iWeb is an application that allows you to easily create your own website and is filled with many cools tricks and features. Click the picture above for a technical writing piece that I created about iWeb.