I think Sportsline does a pretty good job of keeping theirs up to date. Here's a link to the first depth chart on the list. There's a drop-down menu on the upper right to navigate from team to team. If you mouseover the player names an info box pops up.
I also use the depth charts at Football Guys. I have no idea how up-to-date it is, but it's worth looking at. There is some decent information there as well, although they don't update the info all that often.