Ladies, holla: The iPhone is an excellent tool for a woman who's as organized as a girl scout, but organization is not limited to keeping your schedule of appointments and dinners in order, no no — sometimes you need to keep track of when ol' Aunt Flo is coming (and going).
The Period Tracker App costs $2 and is the ultimate menstrual mentor. You enter in your info, and it tracks your cycles, letting you keep notes about your activities and well being, all the while using twee 'lil hearts and flowers to denote important days (to be fair, "ovulation" would be too long to fit in those boxes).
Don't have an iPhone but still need a period tracker? Use the website Mon.thly for free.