You can also use iCal instead --
Just create a new event to repeat daily or hourly at whatever interval you want, and instead of choosing "send me an email" or "chime at me" for the alarm you can have it "Open File" and have it run your script. When you save the applescript you should save it as an "Application" rather than as a script, then do the above using iCal.

I wrote a script for processing the inbox on the mac desktop (along with others), and as one of its features, it closes whatever web browser someone is using if the person is processing a web-item from their inbox. I just drag webpages to this inbox folder on my desktop; and when I process them the script keeps me focused instead of getting lost in cyberspace.

It's accessible here. A rather large download (~100MB) because it is a full GTD implementation for the mac -- and contains three Quicktime movie tutorials on juggling the 9 core GTD habits.

http://homepage.mac.com/toddvasquez/apps

Todd V