I recommend checking out the recurrence dialog in the Stickies app (http://www.zhornsoftware.co.uk/stickies/) -- it provides for daily, weekly (time of day, weekdays), monthly, either by day or "nth weekday", and yearly (date). (I can send a screenshot by request, or just install the program -- it's quite useful.)
Also, I agree with the suggestion to allow setting negative days of the month, to allow "last day" or even "n days before last day".
I recommend checking out the recurrence dialog in the Stickies app (http://www.zhornsoftware.co.uk/stickies/) -- it provides for daily, weekly (time of day, weekdays), monthly, either by day or "nth weekday", and yearly (date). (I can send a screenshot by request, or just install the program -- it's quite useful.)
Also, I agree with the suggestion to allow setting negative days of the month, to allow "last day" or even "n days before last day".