Today I installed a new theme that I really like. It's basically an improved version of the numix theme that everyone seems to love. If you love the numix theme, then I think you would love this.
Below is a preview of the theme, but I chose to install it without the icons.
Download the theme from here. Unfortunately, I needed to sign in with my dropbox account, but hopefully you already have one as well.
Create a themes folder if it doesn't already exist.
Extract the theme to the folder you just created. (This assumes you downloaded it to your downloads folder rather than clicking the option to add it to your dropbox).
mv /home/$USER/Downloads/Ultra-Flat-Theme.tar.gz $HOME/.themes. cd $HOME/.themes tar --extract --gzip --file Ultra-Flat-Theme.tar.gz
Install unity tweak tool if you haven't got it already.
sudo apt-get install unity-tweak-tool
Open unity tweak tool and select "theme" before clicking on "Ultra-flat"