I believe 'gnome-session-properties' is what you are looking for. It has a tab called 'Startup Program' where you can add such apps you want to run at GNOME startup.
open the gnome control center, go to 'advanced' and open 'Sessions'.
You can just add programs to the list under the 'startup programs' tab.
The syntax for Gnome session startup programs are strick:
I.e., the following commands will fail:
/usr/bin/numlockx on & LANG=zh_CN.GB2312 /usr/bin/chinput
Only this can work:
/usr/bin/numlockx on /usr/bin/chinput
Also remember to set the order very high, e.g. 75, so it starts absolutely last. If you dont do this, it hangs things and gives problems.
documented on: 2005.05.05