I love my LibraryElf.
My Elf sends me emails about
- what hold's are waiting to be picked up,
- what's overdue,
- what will become due in the next 3 days,
- what isn't due (but what day they are due),
- and my holds that aren't in yet (including my place in the holds list.)
My Elf account can include multiple users, so that one email tells me about all the cards in my household, as long as I know the account number and PIN.
I love it. It's easy, convenient, a nice reminder of what is and isn't due. And, by not deleting old emails, I can use it to track all the books and DVDs I've checked out of the library.
Some libraries are including information about the LibraryElf on their website.