To use this script, put a list of files you want to back up in /var/mobile/backuplist. It will copy them to /var/mobile/backup/, tar and bzip2 them, then scp them to your computer using ssh keys, which I explained earlier. It could obviously use regular scp if you don't mind typing the password.
while read line; do cp -r $line /var/mobile/backup/; done < backuplist
tar -cf backup.tar /var/mobile/backup
scp -i ~/.ssh/KEY ~/backup.tar.bz2 USER@IP:/PATH/TO/DESTINATION
rm -rf backup