There are many great applications available for Apple's OSX. Few are expensive and many are free.
Vienna
Open source RSS reader. Get it here.
Mac Apps
Hallon
Much more than a bookmarking application, it is a true document marker, recognizing songs in iTunes, web pages, Text documents.
Hallon can create bookmarks in many applications (like iTunes) that usually can't create bookmarks and they are always accessible from a menu whatever you are doing. You can e.g. bookmark your favorite songs, an email that you have to reply to later that day, some documents that you are working on or the contact information of a friend whom you need to call before the end of the week.
And it's open source. Get it here.
Books
An open source book organizer. Learn more and download from http://books.aetherial.net/wordpress/
Sandvox
I have started using Sandvox by Karelia to build my websites. While it is still in beta (I like living on the edge) I find it very useful. It is well designed as well as aesthetically pleasing, sporting a true WYSIWIG editing of your content.
In addition, its architecture naturally lends itself to extension, both in terms of design as well as components. In fact, I was able to develop a simple "pagelet" with which Amazon Affiliates can easily add product links to their site.