Gnome Tweaks

Some of these could already be in effect depending on your distribution. Launch the configuration editor from Applications->System Tools->Configuration Editor or by typing gconf-editor in a terminal. Go down the tree to the following:

/apps/gnome-session/options

Here you can disable the show_splash_screen option for a login boost. Now go to:

/apps/metacity/general

Enable the reduced_resources option for a significant speed increase. A little further down the tree at:

/apps/nautilus/preferences

You can disable show_desktop to stop Nautilus from controlling the desktop. Of course this means that you won't get icons or a right-click menu on the desktop. Then, travel down to:

/apps/panel/global

Disable enable_animations and highlight_launchers_on_mouseover. Finally, if you append the following line to your ~/.gtkrc-2.0 file (create it if it doesn't exist) you remove GTK menu delays.

gtk-menu-popup-delay = 0