Eclipse
I have a new favorite development environment: Eclipse. It really is a unique approach to creating Java applications. What I like the most is the SWT, which is an alternative to Swing. It runs so much faster than Swing, mostly because of the unique way that it handles rendering the UI components. It could use a little more documentation, but otherwise, Eclipse has definitely gained favor from me.
Disclaimer: Any viewpoints and opinions expressed in this article are those of Nicholas C. Zakas and do not, in any way, reflect those of my employer, my colleagues, Wrox Publishing, O'Reilly Publishing, or anyone else. I speak only for myself, not for them.