Google has introduced tagging (bookmarks) to its personalized/search history functionality, which can also now be added as a content module to the personalized home page (Fusion). This new tagging capability allows users to create a directory of sites, which can also be annotated.
When browsing your Search History, just click the star next to one of the search results listed to create a bookmark for that website. Once you've starred a site, you can click the "Edit" link to add labels and notes for the site.
Furl, del.icio.us and MyWeb all share a "social search" dimension — users can see what others have saved (Jeteye takes this concept further in interesting but complicated ways).
It will be intriguing to see if Google tries to move into this social search realm as well.