Recently, I came across something neat on another forum.
http://wastedonsteam.com/What this is is you enter in your steamid (the url for your steampage with only the last part) and it will shell out how much total time you've spent on steam. It also displays your most played game with how much percent of your steam time it's taken up. Another cool thing is that it also gives you some visual piecharts that shows how much your other games account for your total playtime.
so here's me:
crab_f
is ranked #269 By hours played
Has 5139.2 hours of playtime. Their most played game is Team Fortress 2, with 4290.7 hours played, which accounts for 83% of their total playtime.
Yet another cool thing is on the left-hand side, when you scroll down, you can click games that you own and see where you stand in most played for the game.
I'm ranked #38 on tf2, ranked #9 on the original Quake, and ranked #7 on Titan Quest, among other games.
So what about you guys? How much time have you wasted on steam?
(also, apparently some anti-virus programs might say the site "is linked to malicious content," but don't worry about it. The site is connected to the Steam API and you don't have to log in to use it.)