The SPL recently upgraded their catalog service, and one of the new features is RSS feeds. I was trying to find Jonathan Safran Foer's new book, Extremely Loud and Incredibly Close, but it's not yet listed by SPL. But now I can subscribe to an RSS feed of all works by Foer, so I'll know right away when his new book is available.

It's trivial to aggrigate the feeds of several searches, thereby creating a true watch list, since SPL allows boolean OR searches. Here's a feed for all items by Foer OR by Philip Roth, for instance. Only a limited number of hits are returned by the RSS feed, so it's probably not too scalable if you want to watch a large number of artists (especially artists who create different types of media). But it's a great tool that doesn't use anything but SPL's own search and RSS features.