I love TiVo. In particular I like their wishlist search. You can search for a movie or TV show you want to see by keyword, title, actor, etc. And even if it's nowhere to be found in TiVo's two weeks of guide data you can still create a wishlist out of it. Then anything that matches your search in the future will automatically be recorded.
collection of controls you'll always see a "Subscribe via RSS" link in the lower-left hand corner. And just like TiVo, this even works when there are no results to be found.
To take this a step further I'll soon be creating statistics that registered SilverlightXAP developers can view based off of these subscriptions. The idea is that developers can view popular searches and see what people are looking for. They can then create a control that a bunch of people want, and those people will automatically be notified when the control is published.