Just noticed my hosting service offers cron jobs (that's lewd.) (Actually, it can be worse than lewd. In the right hands, it can be quite an annoyance!)
Anyway, always wanted to set one of these up. Wasn't much documentation, but with a little Googling, I was able to figure out what to do. This site was helpful:
Using cron to automate tasks (4webhelp.net)
With the interface provided by my host, this is all the syntax I needed to run my file 'cron_test.php':
/usr/bin/php -q /usr/home/USERNAME/cron_test.php