For me - I grab all kinds of SBM sites such as Digg, SU, BackFlip, Spurl, etc. and bookmark the articles that I write. There is a Google Bookmarking site - but I've never heard of a Bing Bookmarking site. Interesting question though.
Interesting question, yahoo's bookmark manager is located at bookmarks.yahoo.com. google's is located at google.com/bookmarks. There is no corresponding server dns entry for bookmarks.bing.com. It simply goes to bing.com. I guess the functionality for bookmark management isnt available in the bing portal as of now.