Can anybody explain in simple English what is the pubsubhubbub thing about? Is it just another pinging service like pingler? With the availability of a WP plugin for pubsubhubbub http://wordpress.org/extend/plugins/pubsubhubbub/ how is it different from a regular pinging service? How can I find uses for it? How is it different moreover's RSS feed aggregation/filtering service? Are there any commercial and/or free utilitarian services built on PSHB?