iCal’s alarms come in handy for those of us who tend to forget the various little things we always need to do. However, you may find iCal getting cluttered with such regularly-scheduled events, pushing other events out of view. But there’s a simple solution to this problem.
Go to File » New Calendar » On My Mac, and name the new calendar Reminders or something similar. Put all of your reminders in this calendar, and make sure they all have alarms. Then, simply click on the checkbox next to the Reminder calendar in the sidebar to hide the calendar. Alarms for the hidden calendar will still go off, but all your miscellaneous reminders will no longer clutter your iCal window. (This “hide in other calendars” strategy is useful for other things as well.)
Via Mac os X hints