If you are using Widgets you can use the Pages widgets, otherwise take a look at the template tag, wp_list_pages().
What MichaelH said. Check and see if your theme supports widgets (95% of them do) by going to “Design” than “Widgets”. I will warn you that if you start playing with adding widgets to your sidebar it will knock out the sidebar configuration that’s currently there, all you have to do then is add them back using thier corresponding widget. The upside to that is you can decide what sidebar items you really want and place them in the order you would like.