CataList allows professional readers, like librarians, reviewers, and book retailers who are logged into the system to request advance reading copies (ARCs) of books. While CataList hosts the ARC request feature, it is up to the book's publisher to decide whether or not reading copy requests are fulfilled.
NetGalley is an online digital galley provider that connects professional readers (such as library staff, media, bloggers, etc.) with publishers' forthcoming titles for promotional purposes. NetGalley offers free accounts for different types of readers, and after creating your NetGalley account, you too can "read, review, & recommend" all sorts of books (and earn a few badges!). You must fill out the required "bio" and list your favourite genres in order to make requests.
CataList supports a direct link to title request pages on NetGalley when ARCs for the title are available – but the two products are distinctive services and require separate logins. Before you can request ARCs on NetGalley, you need to sign up for a NetGalley account.