If you send holiday cards each year, keeping your addresses in spreadsheet form on your computer will save you loads of time. Each year, you'll just need to update addresses for those who have moved, remove people you no longer want to send cards to, and add new friends. This process is easy when you use your computer. Plus, when you have your address book in spreadsheet form, you can print address labels and eliminate the task of hand-writing addresses on each card. Instead, save your energy for writing a personalized note in each card (instead of addressing them).
Here's an example of a spreadsheet layout (using fictional names and addresses):