Twine empowers collaborative sharing and search using the Semantic Web to uncover and tie together concepts and deeper-than-textual relationships in Web pages.

A commented and tagged linksblog with reference counting, Shared Stuff also shares my Google Reader profile. Like Faves, it can also share via e mail, but responding requires a Google login. Google plans to shutter Shared Stuff 2009 March 31 and perhaps move items into Reader.

A Semantic Web innovator, this flexible and powerful linkmarking platform accepts only OpenID and Sxip Identity 2.0 logins. Groups can host discussions distinct from linkmark entries. It also publishes hFolk and hReview microformats. Its tags feeds my Ideavine and Claim ID sidebar tagroll. Unfortunately it suffered a severe data loss in January 2009 and its founder Larry Halff took it offline. As a premium subscriber, i hope and expect its phoenix Magnolia 2 to rise again this spring and resume an invitation only service.

A most powerful and flexible linkmarking platform, and unlike others, Faves (formerly Blue Dot) requires no registration. To lower the barriers of use, it saves user identity in a browser cookie and invitation identities in a coded link sent via mail. Recipients need not register to reply. The coded link also establishes a friend relationship with the recipient, should they also join. Those who login can group friends and share specific links only with those groups. Faves feeds my Tribe and Gaia summaries and other tumblelogs, and marks items i feel worthy of my readers.

Yahoo has released, and also bought many often internally competing, projects that have failed to gain popular following. Though MyWeb 2.0, a revamp still in beta, has rich features, it lacks such popularity. Among a dozen linkmarking sites, i use it to annotate and share pages with groups and services already with users at Yahoo, such as my Yahoogroups.

A social and collaborative linkmark sharing site, Delicious features a rich Web programming interface, informative graphic design, and desktop applications such as Cocoalicious. Though Delicious may be social, it lacks some features for communications. It limits notes to 1024 characters, cannot capture images, cannot generate mail nor invitations for guests, does not support OpenID nor discussions. When Delicious published an add-on extension for Firefox, i began using it instead of Firefox Bookmarks. I also used it to share between Firefox and Flock. Then when Foxmarks debuted, i reverted a bit and still use it to share with friends and readers, but for that purpose i prefer more feature-rich services, tagged “linkmarks” here.