I found a cool tool that you can use to keep track of all of your library cards and items checked out at any library you may attend.
www.libraryelf.com is a tool in which you type in your library card numbers, and in turn it will tell you in various formats (calendar, list, etc.) when your items are due. It will even tell you when a book you've put on hold has come in.
I think this would be most useful for a family, because you can type in everyone's card and it will compile everything in one convenient place.
I have added mine to my RSS feeder, so that I don't have to check yet another site daily.
Check it out!