Is it possible to set OS X Leopard to update my system automatically at a specific time, just like Windows does? Right now the Updater randomly pops up when there are updates and I have to manually 'approve' them for download.
You can set up a cron job to do this. Let me find the command to run.
Look up the command
softwareupdate and schedule a cron job to run it.
http://www.thexlab.com/faqs/maintscripts.html -- Info on cron jobs.