For a long time I have thought that the WordPress Administration area could use some beautification. I began my search a while ago and stumbled across Shuttle. From the sounds of it this project is more than just a style sheet. In the mean time, I have installed a new style sheet, SpotPress. I like the change, but do not know if I am going to make in permanent, and I definitely would to recommend it for a regular resolution screen, but it works great on my new wide screen laptop.
Speaking of more than just themes, I am also excited about K2. I knew that just having themes that could easily be changed would not be enough.