We discovered Solarized by Ethan Schoonover and instantly fell in love with its "precision colors for machines and people." Having read up on its properties and unique features we decided to try to make our Ubuntu systems use it as extensively as possible.
Solarized is a sixteen color palette (eight monotones, eight accent colors) designed for use with terminal and gui applications. It has several unique properties. I [Ethan Schoonover] designed this colorscheme with both precise CIELAB lightness relationships and a refined set of hues based on fixed color wheel relationships.
Solarized comes with color profiles for Mac OS X, Vim, Mutt, as well as with color palettes for Adobe Photoshop, Apple Color Picker, and GIMP.

Solarized works as a sixteen color palette for compatibility with common terminal based applications / emulators. In addition, it has been carefull designed to scale down to a variety of five color palettes (four base monotones plus one accent color) for use in design work such as web design. In every case it retains a strong personality but doesn’t overwhelm.
Updated Tim Martin supplied a script that will set your terminal colors directly from the terminal. Copy and paste the following directly into your terminal and the color scheme will be updated instantly.
gconftool-2 --set "/apps/gnome-terminal/profiles/Default/use_theme_background" --type bool false
gconftool-2 --set "/apps/gnome-terminal/profiles/Default/use_theme_colors" --type bool false
gconftool-2 --set "/apps/gnome-terminal/profiles/Default/palette" --type string "#070736364242:#D3D301010202:#858599990000:#B5B589890000:#26268B8BD2D2:#D3D336368282:#2A2AA1A19898:#EEEEE8E8D5D5:#00002B2B3636:#CBCB4B4B1616:#58586E6E7575:#65657B7B8383:#838394949696:#6C6C7171C4C4:#9393A1A1A1A1:#FDFDF6F6E3E3"
gconftool-2 --set "/apps/gnome-terminal/profiles/Default/background_color" --type string "#00002B2B3636"
gconftool-2 --set "/apps/gnome-terminal/profiles/Default/foreground_color" --type string "#65657B7B8383"
Deprecated! Gnome Terminal can be a bit tricky to colorize since the application cannot import color profiles/themes. The easiest way of getting Solarized to work with Gnome Terminal includes some light work in the Gnome Configuration Editor, gconf-editor.
Start the configuration editor by hitting ALT+F2 and typing gconf-editor.
Open up the following folder in the configuration: /apps/gnome-terminal/profiles/Default
Uncheck use_theme_background and use_theme_colors.
Find palette and change the value as illustrated below:
#070736364242:#D3D301010202:#858599990000:#B5B589890000:#26268B8BD2D2:#D3D336368282:#2A2AA1A19898:#EEEEE8E8D5D5:#00002B2B3636:#CBCB4B4B1616:#58586E6E7575:#65657B7B8383:#838394949696:#6C6C7171C4C4:#9393A1A1A1A1:#FDFDF6F6E3E3
Change the value of background_color as illustrated below:
#00002B2B3636
Finally change the value of foreground_color as illustrated below:
#65657B7B8383
Close down Vim and copy the solarized.vim file into your Vim settings directory:
$ mkdir -p ~/.vim/colors; cp solarized.vim ~/.vim/colors
Now open up your Vim configuration file:
$ vim ~/.vimrc
Add the following to the top of the file:
syntax enable
if has('gui_running')
set background=light
else
set background=dark
endif
set t_Co=16
let g:solarized_termcolors=16
colorscheme solarized
Eclipse requires you to download the Eclipse Color Theme plug-in before you can use the Solarized theme.
Once you have downloaded and installed the Eclipse plug-in you can download the Solarized Dark and Solarized Light themes.
Several other syntax highlighters and adaptations of Ethan's Solarized exist, if you cannot find a scheme for your tool of choice, make your own and let Ethan know what you have contributed!
Kudos! Thanks to Otis Bean for pointing out that using gconf-editor is the right way to go about editing configuration files.