ROBK  I don't think this program is needed at all if you run Leopard as the Leopard launchd should run skipped jobs when the machine is next awake.

But if you are still running Tiger, this program should do the trick and make sure your computer is running the unix maintenance scripts at a regular interval.  
(Version 1.5)

SARGASSO_C  This program is probably the easiest CRON script executor to use, that I have found. Follow the installation instructions, if you want to run CRON maintenance every time you restart, or just use it like a normal application, once in a while, like I do. It is a small, script file, so it is easy to download and to share. Previously I have used Cocktail and Maintain, both have their faults - Cocktail is updated far too frequently, doesn't repair permissions as well as it should, and is rather expensive as far as shareware goes - Maintain is too technical for most users, and has a lot of features which look far too dangerous for the average user to meddle with. PsuedoAnachron is is just a plain CRON script executor, nothing more or less. And that is why I like it.  
(Version 1.4.1)