A gentleman named Lambent Stew has put together a webpage that gathers some of your Steam data and arranges it like little quantitative ducks in a row. How nice.
There are a number of homemade utilities that reconstitute Steam information, like a Steam sales tracker, and a Steam account value calculator. What's unique to this one is it outputs some useful aggregate data, like total hours played, and what percentage of games you've bought you haven't opened, you jerk. Good lord, I haven't played 1,006 games. Tonight, Nancy Drew: Ransom of the Seven Ships, it's you and me.