House style for GUIs.
Slight detour from the usual stuff directly about Java, but one of the things I've been thinking a lot about lately is having a house style for GUI applications. There is a real pay off in terms of recognition, as long as people like it.
The best example of this is Apple's brushed metal style. You can spot an Apple application from half way across an office, especially if it's running on a PC.
I've just started using Napster for downloading legal music, and the look and feel of that is very much all it's own. However both of these examples are good because they are not "in your face" about it.
To the degree that we can, we've been developing a house style, but there's still a ways to go. But it's something to think about.