If you use startx, you should be able to put it in your .xinitrc file. Put it before the DE/WM start up. Here is mine for an example:
Code:
# Duron 950 box "uilleann" user fancy .xinitrc file
# Start the stuff I want to run when I startx
# The artwiz-fonts sometimes conflict with your locale settings. To get
# them to work you may have to put the following at the beginning of your
# .xinitrc file
# export LC=C
# export LC_ALL=C
# exec gnome-session
# exec kde
# Esetroot ~/backgrounds/linux.png &
gkrellm -w &
# This will run a screensaver as your background
# /usr/X11R6/lib/xscreensaver/hopalong -root &
xscreensaver &
exec fluxbox
