Signing up is easy, you use an email address and a password you choose. Once you have registered, you can choose one or more libraries. You must tell them the user name and password that you would use to log into the online catalog for that library. For CONSULS, this would be your ID number and your library PIN. CONSULS is listed as the Connecticut State University Library System, under US Libraries. There are also many public libraries and a few more academic libraries in the US, Canada, and a couple of international libraries. Library Elf also accepts requests for new systems, so just email them. (This is how I got CONSULS on the list!) Just about any library system that allows you to check your records on the web should be accessible to Library Elf.
The biggest difference between this service and the email notices that you get from the libraries themselves (if offered) is that you can get notices 3 or 7 days before the book is due. (So if you only go to a particular library once a week, you can get notified what will be due before you go!) And you only have to check one site if you use more than one library.
If you use a request system, such as the Intercampus Loans (Request a book) in CONSULS, you can get email, RSS or text messaging notices when your holds are available. Here is a picture of the text message I got for one of my requests, Net effects : how librarians can manage the unintended consequences of the Internet / edited by Marylaine Block.
Originally uploaded by rch.
One word of warning: Library Elf is in beta. This means that they think that it is stable and reliable, but there may still be bugs in the system. You should not completely depend on this or any system, beta or not, and Library Elf is not responsible for any fines that you get because you missed a due date. It's a great product, and one that I intend to use, but your loans are your responsibility.
Oh yes...unless your library checks out Interlibrary Loan books in their Circulation system, you won't see those. (If you aren't sure, ask the library you get ILL's from, or log into the online patron record and see if your ILL books are listed.)
Happy Holidays with your Library Elf!