If you're a sports fan, I would recommend an app made by Google, but sadly it doesn't exist anymore! I LOVE the app Scoreboard, which Google first made sometime in early 2009, I believe, but seemingly went without updates for the last two years.

It's funny, the app worked like crap on my G1 and Nexus One, despite being a pretty simple app (it just notifies you of scores for teams you ask for). But now that I have my Galaxy Nexus it works beautifully, and way more reliably than it used to! Very weird.

Fortunately, it gets reinstalled when I log into a new phone. When I recently wiped my GN to put Jelly Bean on, it was automatically pulled back down when I logged in, which is pretty neat...