ZbigniewLukasiak's social bookmark management site.
Unfortunately seems defunct.
The goal of this project is much more than a ChangeAggregator. I hope that you can base ratings on it - and the advantage you have over other schemas is that you start with some existing economy of attention (TheAttentionEconomy) so there is a hope to come with some more balanced and meaningful model. This rating would be a direct amendment of the Google PageRank - it would be still ranking by number of links, but those links would be constrained to some meaningful category, i.e. the links you want to watch for every change.