As you might have heard, LibreOffice has been accepted for this year's Google Summer of Code program. I am a mentor or a co-mentor of several tasks, but one of them is the closest to my heart, and that is the UI Cleanup task.
Please consider applying for it - in the summer time frame, we can do a big change. And it is better than that, this task consists of several smaller sub-tasks, each of them few days to a week long, so you can see the results of your work immediately, and the big change is in fact result of all those smaller fixes 'here and there'.
If you are one of those who looks at the screenshots first, this is a task for you :-)