Cronjob is a time-based scheduling service in Unix-like computer OS. Cronjob are useful for periodic tasks like updating content, sending emails, refreshing database and more commands that need to run periodically. Here's some free cron jobs services: - SetCronJob - http://www.setcronjob.com/ You can create up to 10 cron jobs, running up to every five minutes. When the time matches your criteria, SetCronJob will call the URL given (script in PHP, ASP, JSP, etc, backup your files, databases, clear temporary files, send newsletters, etc). - OnlineCronJobs - http://onlinecronjobs.com/ The purpose of this website is to allow website administrators without cronjob service on their own host, run cronjobs. - CronMe - http://www.cronme.org/ Free web cron service is that enables you to setup your own crontabs with web interface and lets you to execute any URL on specified time/date. - CronJobs.org - http://www.cronjobs.org/ The easy way to execute automatic tasks on your website. - CronLess - http://www.cronless.com/ Cronless is a free cron job service. We provide free access to a simulated linux cron job, it does the same thing, just in a safer and easier method. And many more out there, but I think that's enough for you
...and another one: callmyapp.com - callmyapp is free (of course) and designed for application developers and supports a RESTful HTTP API. It will repeat callbacks with a minimal interval of 60 seconds - which should be enough for most uses! (callmyapp is an apihouse.com project).