BitPal is an Address Book and a To Do task manager. It's really nicely designed and easy to use. And it's designed to be mobile.
Drag the BitPal folder to your USB Pen Drive, and everything you need goes with you. Take your address book info to work, while keeping it off company computers. Have your To Do List in the palm of your hand.BitPal, Inc.
Sounds like a great application, and it works with OS X and Windows XP. From the look of it, I don't think it integrates with Address Book or the equivalent on Windows. If it did that, I'd get it for Kate. Oh, and can we add calendaring, too?