Reeder is a fantastic RSS reader for Mac, which syncs perfectly with Google Reader. It has built-in support for Zootool, which makes it possible to save links in your Zoo while reading your favorite RSS feeds.
You should also check out Reeder for iPhone and iPad.
Fluid is the perfect tool for Mac to create nice looking desktop versions of web applications. Here's a little instruction on how to build your own "Desktop Zoo" in seconds without writing a single line of code.
For all PC and Linux users there's a nice alternative to Fluid called Prism. Prism comes from the awesome Mozilla guys and does basically the same as Fluid - providing a desktop version for web applications. They are even so close that the installation process is 99% identical. So please just refere to the list above and create your own Prism app now.