Came across this page that lists the best open-source software for the Mac. I tried out some of them. Yes, I had something better to do, but I didn't feel like doing it right then.
Camino (web browser)
This thing is supposedly based on Firefox but customized for Mac performance. Noticed that it loaded up lightning fast (I think even faster than Safari) which was good. Also noticed that it looked very much like an Apple application (Mail 2.0) - which was also good. Then I opened up Slashdot and saw that something was missing. No orange icon anywhere. This thing doesn't support RSS feeds; even though its supposedly based on Firefox 1.5. Good bye, Camino. Back to Firefox.
Vienna (RSS Reader)
I was amazed at this piece of software. Replaces NetNewsWire for me instantly. It has all the standard features you'd look for (3-pane window, internal tabbed browsing options, spotlight-enabled search) but it has a few extras too. The one I liked most was that it has "Smart folders" - you can aggregate collections based on a variety of options. So if I'm a die-hard iPod fan, for instance, I can make a Smart folder that aggregates all of today's stories with the subject "iPod" in them. Or if I like to mark articles to read later, I can have a smart folder that contains articles about "intel virtualization" from the past week that I've flagged. Awesome stuff. All free and open-source. Good-bye, NetNewsWire.
Freemind (Mind-mapping tool)
I really liked this tool to organize hierarchical information. Its based on Java, so runs on any platform (a big plus). Unlike most other Java apps I've seen on the Mac, this one is very responsive - probably because they've made the GUI in AWT rather than Swing. Nothing says it like a screenshot, I created this map of a course project I'm doing:
It could probably be made to look far better and the interface leaves much to be desired, but I think I can put this piece of software to good use. You can even export this to HTML with folding/unfolding options in a list interface, see this example.