Customizing WordPress - what do you want?

Hi folks! It's not often I start a new topic so this is a rare treat :wink:

I seem to have volunteered myself for a series of articles on WPMU.org about customizing WordPress and want your thoughts!

Things that spring to mind are;
- white-labelling WordPress
- customising login/register forms
- tweaking the editor

But what customizations are you looking for? The idea is that I take your suggestions, figure out how to do it and then write up a how-to to be published on WPMU.org.

So, what do you want?!