The real gem would be if you could find a way to figure out what they might want to be notified about without them having to specifically request it. For example, say I want to know when 24 is coming to DVD, but I've only used your site once and I don't think to go and add it. Maybe you can use the Facebook API, see that one of my favorite shows is 24, and then any new notifications relating to 24 get directed to me. This is of course just one example.
This is interesting, and sounds a bit semantic web-ish even :) You could maybe use something like Greenspun's Solar Magnitude Forum to find things that are closer to your interests as well.
Just a thought...