Again is a helper app for Apple's iCal application that lets you easily create repeatable to-do items and show them in your calendar. Again can run in the background so that it's always available and out of your way. All you have to do is add a rule to the notes field of your to-do item using an English-like syntax and Again will do all of the work!
What's new in Again
Fixed the [show] rule so that it doesn't repeat when the item is completed.
Added support for more advanced recurrences, such as on the first weekday of the month or on specified weekdays and months in the year. Check the documentation under "Creating Repeating Rules".