Usually I don't like to waste time tweaking the looks of Ubuntu. But this time I found a theme from Intrepid Ibex that was being tested and planned to be the default theme in 8.10 (not anymore).

I have always looked for a dark theme for Ubuntu, but the ones I found, always had a little detail that would look ugly in some application. This one seems to be perfect. Here's a screenshot:

To have this theme you just need to add the following line to your /etc/apt/sources.lst file:

deb http://ppa.launchpad.net/kwwii/ubuntu hardy main

Now update aptitude and you will have new packages to update. After installation of those packages just go to the theme selector and select the new installed theme. The theme also include some Vista like sounds.