I was looking for a site with good park factors, and discovered that ESPN has great park factor data. Instead of the usual runs and home runs, their data includes specific park factors for HR, H, 2B, 3B, and BB as well. Also, they have the data for each of the past 5 seasons. And it looks like they'll be updating the 2007 data on a daily basis once the MLB season starts.
I think most of us probably underutilize park factors. Sure, when a player switches teams we make some kind of adjustment based on the ballpark he's moving from and the ballpark he's moving to...but do we actually figure out the impact on each of his component stats and how that affects his valuation?
And even fewer of us are using park factors as a major factor in our determination of who to play each week (or each day in a daily transaction league). We may take a quick glance at where our pitchers are scheduled to play, but in theory we should be making park-based adjustments to our projections for all players each week or each day and recalculating their value based on that before we decide who to play each week. The bottom part of our roster (especially in daily transaction leagues) should probably be a rotating door of players facing especially favorable situation (both park and opponent) rather than us using a 'buy and hold' type strategy with mediocre players.
I'm going to have a LOT more to say on this topic over the coming weeks and months.