Which kind of apps? Are them X apps or just shell ones?
If they're shell ones, go to $HOME/.profile and add them at the end. If this file does not exist, be sure make it executable ( chmod +x $HOME/.profile ) and it beginning (in the first line) with "#!/bin/sh".
If these apps are X ones, you'd add them to the Autostart section of your Desktop manager (KDE, Gnome, etc).