Here I'll point you some tips that will help you to use GNOME on computer with a small amount of memory. Long ago 4 Mb was enough to do a lot of tasks; now I can hardly run stock GNOME on my 256 Mb laptop. Here some hacks that I use to reduce memory usage, I hope they will be useful for you too:

• Switch to a simpler theme. Raleigh, Simple or Mist are good in the view of memory consumption. Clearlooks eats too much.
• I shouldn't even need to mention disabling Beagle and compiz.
• Remove as much applets as possible. Each applet takes huge amount of memory (typical around 8 Mb). So the less applets you use the better. I have: menu, workspace switcher, system monitor, notification area, volume, battstat, clocks, task switcher. It's too much heh, but I can't leave with smaller amount.
• I don't use Evolution calendar but I'm fond of Evolution addressbook. So I just deleted it from components:

   rm /usr/lib/bonobo/servers/GNOME_Evolution_Calendar_2.10.server
   rm /usr/lib/bonobo/servers/GNOME_Evolution_Calendar_AlarmNotify_2.10.server

• You'll see Evolution will work much faster
• Delete unused icon themes like crystal from KDE and so on. They actually take a lot of memory and they are scanned on start
• Delete gconf translation in /etc/gconf-2.0, they usually make application start slow. You can leave only your own language.
• Check that gstreamer uses binary registry. This capability is disabled in distribution most probably but it greatly reduces memory consumption by volume applet and by session daemon
• Open session properties and delete some unused apps like egg-cups and pam-panel-icon (fedora-specific hack)
• Remove background if you like, I can't for example.
• Disable spam checking in evolution or better uninstall spamassassin.
• Amazing thing - make a link to /usr/share/locale/ln from /usr/share/local/ln_LN.UTF-8. The point is that gettext first of all searches in ln_LN.UTF-8, then in ln.UTF-8, then in ln_LN and only at last in ln. So you can save a lot of disk searches with a simple link.
• Disable plugins that aren't used. In evolution enable only the plugins you need and remove others from /usr/lib/evolution-2*/eplugins. At least remove groupwise plugins. Disably pidgin and libpurple plugins (remove protocols like gadugadu you don't use for conversations).

• Not everyone will like it but you can also disable icons in menus (Preferences->LooknFeel). It won't save you a lot of memory probably but since icons will not be loaded again and again io cache will be free for other things.

Todo:

• Fix 9 mb for battstat applet
• Fix 22 mb for pidgin (delete logs probably?)
• Fix huge memory consumtion by gtk widgets. Simple applet dialogs usually takes up to 5 Mb.
• Disable nautilus?
• Fonts stat on startup - remove unused fonts (need to check with latest fedora)
• Avahi not used
• Kerberos (from gnome-vfs?) not used
• Disable looking into .local for everything not used

Measurements with exmap

• (This section added by RodneyLorrimar) Exmap is a tool which can give fairly accurate readings of an application's memory usage. It was demoed at GUADEC 2007.

  This page contains measurements of the memory savings gained by implementing some of these suggestions, and provides a procedure which can be followed to execute your own tests. In summary, you can save:

  • > 500kb by using "Simple" instead of "Clearlooks"

  • 4500kb by removing the Evolution calendar component
  • about 2500kb-3000kb by removing all libpurple protocol plugins except the one you use
  • 38500kb by not using trackerd and the Tracker applet (tracker is an equivalent to beagle mentioned above)