Create a household excel document on Googledocs. You can share this with your partner and when your kids are older it can be shared with them too. Create different tabs for different things you want to keep organised.
Events: This is where you add events, school events, extracurricular classes/activities, family visits, play dates, family holidays and activities for half term etc..
Meals: This is where you can keep meal-planning for the week organised.
Bills: This is where you can keep track of everything on a monthly basis along with outstanding balances, when it was paid etc..
House maintenance: This is where you can keep weekly chores and divvy up among the household. This is also where you can keep annual/seasonal list of things to do in the house. For example: Clean gutters, clean fireplace etc..
Wardrobe: This tab keeps track of things your children already have and helps keep track of what you need to shop for.
Christmas list: A running list of items that are on your children’s wish list as well as a list of people you have to shop for.
Baby schedule: If you have a baby, you can keep a list of monthly milestones; feeding schedules etc..