If you've not discovered it yet, check-out alltop.com. It is Guy Kawasaki's aggregation site that is a beautifully designed, very handy directory of all the top sites on the net (including PFRE as of today ).
For example, there is a page for every major subject they list and the Photography page lists all the top photography sites and blogs. This is a great way to find blogs and sites that you've never heard of before. Alltop.com is one of my favorite sites.