I built a service that tracks new music releases because I got sick of missing things from the artists I was interested in (http://beathound.com - iTunes only for now) - it only emails you at most once a week, so I use it generally once a week.

As it has grown, it's been interesting to observe the parts of it that I work on a lot (the parts I use - I just today fixed a bug in something that I kept seeing in my weekly emails) vs. the parts that get neglected because I don't see them as often.