I feel sorry for Java Swing apps sometimes (I don't want to get into a discussion about bloat here, cause I'm not really talking about it). Python is immune from it because it doesn't really have a gui library (I've even heard Guido say that guis are provided for better by 3rd parties than being in the core libraries), unless you count tkinter apps (though many distros don't even ship with that enabled).
Why do I feel sorry? Because Swing apps are not native to any one operating system, you don't hear about them very much (java editors/ides might be the sole exception). Even the useful ones. They aren't marketed. No one wants them. Open source "purists" neglect them because java is not "free", or the widgets don't look right, or the integration with the desktop is missing. Non-technical users don't want to install a runtime engine.
Just the other day at work, someone asked me for my thoughts on a subject and I sent a screenshot of a mind map I made with freemind. A few people asked me later about the tool. Freemind is a useful tool for brainstorming or outlining (could use more polish but as is it is functional for me), yet not shipped with Linux distros. It also runs on Macs (which lack mind mapping software) and windows (if you don't want to pay for mind mapping software), and anywhere else you have a jvm 1.4+.
Any other useful swing apps out there that more people should know about? What about you Apple people out there, do you use swing apps? FYI (there are "native" kde mind mapping tools, kdissert and vym if you don't want to pollute your desktop ;) )