Not trying to spam links on here constantly (Last one for awhile) - but this one I felt could really be used by everyone here - http://10k.aneventapart.com/1/Uploads/91/
Don't let the link name fool you.
I did one for an example of the forum homepage - http://zurb.us/rHWG0A
Basically on the first link you enter the site name and then once loaded you drag little boxes around areas you want to comment and leave a little note. Stuff like "this rocks" or "fail.".
Personally I think I will start using it for showing others new designs and highlighting areas that I can leave a comment asking them spec. what they think about that area alone.