Old laptop + Ubuntu

Install minimum only base system. (you can use the server/alternate cd)
sudo apt-get update
sudo apt-get upgrade

sudo aptitude -y install xserver-xorg-core xinit menu menu-xdg jwm fluxbox alsa-utils mrxvt-m

# sudo aptitude install jwm
# sudo aptitude install fluxbox
# sudo aptitude install fvwm-crystal
# sudo aptitude install icewm icemc wmctrl
# sudo aptitude install --without-recommends lxde
# sudo aptitude install xfce4
# sudo aptitude install gnome-core
# sudo aptitude install kde-core
# sudo aptitude install kde4-core

first, put the lxde repo into /etc/apt/sources.list :

# sudo nano -w /etc/apt/sources.list
# then paste this line into it:
deb http://ppa.launchpad.net/lxde/ubuntu hardy main
# then:
# sudo aptitude update
# sudo aptitude install --without-recommends lxde

Browsers
sudo apt-get install firefox

Plugins
sudo aptitude install flashplugin-nonfree sun-java5-plugin
sudo aptitude install ubufox adblock-plus firebug firefox-greasemonkey firefox-webdeveloper

# to make plugins works for firefox 1.5 or swiftweasel
cd /opt/firefox/plugins
sudo ln -s /usr/lib/flashplugin-nonfree/libflashplayer.so
sudo ln -s /usr/lib/jvm/java-1.5.0-sun-1.5.0.15/jre/plugin/i386/ns7/libjavaplugin_oji.so

Other:

# other stuffs
sudo aptitude install openjdk-6-jdk pidgin gkrellm wine qemu gxine xarchiver evince
# tools for desktop
# sudo aptitude install conky
# sudo aptitude install gkrellm
#
# stuffs i like, tools i use
# sudo aptitude install zim

Great url http://knol.google.com/k/ubuntu-minimal-desktop-installation-guide#