It would be great if there could be a view where one could see sites almost like categories. Each site would have the number of bookmarks in that folder and clicking on it would open a view that was just sites from that domain.

This might be done on a most to least frequent basis - e.g., if I have 100 bookmarks of css-tricks.com and 1 bookmark from wargamer.com, css-tricks would appear above wargamer.

Because the list of domains could get excessively long I'd also suggest that after say the first x domains (50? 100?) there be a "More" option which would allow one to see more domains.