(I posted this recently on the Friends in Tech blog, but thought you might find it useful, so I am reposting here. -- Douglas)
When you are as much of a bibliophile as my family, it can be a trial to manage all the books you have checked out and those you have on hold, waiting to be delivered to your local library. Add to this a spouse who is engaged in the final stages of a Ph.D and you have the makings of an organizational nightmare. This is what makes it such a lucky chance that I discovered Library Elf a year or so ago.
Library Elf, in cooperation with hundreds of libraries across the US, Canada Australia, New Zealand and the UK, allows you to collect information for each card you manage and combine it into one, easy-to-use, interface. If your library is included in their list of compatible library systems, you can enter your library card numbers and login information. Then, regardless of the online services your library provides, you gain automated web and email notifications of due dates and books on hold. Library Elf also provides RSS feeds, if you prefer to receive your notifications that way.
If you have a family-full of library accounts to manage, Library Elf can help to make your life a bit easier and also save you some money on late fees.