Ryan North has beefed up RSSpect, which was a quality service to begin with.
We’ve just added a brand new type of feed: AnySite feeds, which allow you to turn almost anything online into RSS, even websites you don’t control! All you need is a URL.
We’ve just added a new feature called Web Alerts. Now your RSS feeds can double as a mailing list, and you don’t have to do a thing. Your mailing list is activated as soon as someone signs up for it, and we’ve given you the code to let readers sign up right on your site.
AnySite feeds apply to documents as well, which I think is the great part. If you want to know if a certain pdf file gets updated, or an mp3, or anything else for that matter, you can snap an RSS feed onto it and get notified when it changes. Neat!