I use this one - http://tutorials7.com/go/flatadmin
- it is called Modern Admin and it really gives you a lot of functionality! It is flat-retina ready template for Wordpress admin. This plugin comes with 4 color schemes, custom login form, configurable menu & dashboard icons.
Here are the features of this great plugin:
1. Clean design and retina (like on Apple :-)) support
2. 5 color schemes: Blue (default), Green, Red, Yellow, Purple (and more free color in the future)
3. Custom login
4. Custom logo text/image
5. Choose your own icons