I believe that the move by Google to adjust public page ranks for uncertain reasons (that do not appear to be related to actually "authority") that a market opportunity has been created. I think it would be a great move to create a Page Authority rank along the lines of the authority of pages pointing to a page. Page Rank is often overstated in importance but it is an interesting figure to see. Since the Google one now seems to be inaccurate (for the way most people want to use it) a market exists for someone willing to provide such a rank. Lets just take ove very obvious example - the home page of the Washington Post has a pagerank of 5. My management improvement blog has a page rank of 5. That is obviously totally misleading, the Post has much more authority - even if all you do is use the linking behavior on the web.
The task would require some smart programming and a fair amount of computing power but I think is within the power of many people. I wish I were one of them, I would do it.
Related: Google Pagerank Update - Innovation and Google