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, though of course, responding requires a Google login.

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 Claim ID sidebar tagroll.

A most powerful and flexible linkmarking platform, and unlike others, Faves (formerly Blue Dot) requires no registration. For minimal functionality, it saves user identity in a browser cookie and invitation identities in a coded link sent via mail, so recipients need not register to reply. The coded link also establishes a friend relationship with the recipient, should they also join. In addition, members can group friends, and share specific links only with those groups. It 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, Del.icio.us features a rich Web programming interface and desktop applications, such as Cocoalicious, and informative graphic design. Though Del.icio.us may be social, it also lacks features useful for communications. It limits notes to a few hundred characters, cannot capture images, cannot generate mail nor invitations for non-members to specific links, does not support Open ID nor discussions. Since Del.icio.us published an add-on extension for Firefox, in place of Firefox Bookmarks as the main linkmarking service, i keep Del.icio.us marks mainly for my own use, and to share between Firefox and Flock. Though not a top priority, i also share for friends and readers, and rarely lock down my links. For sharing links, i prefer more feature-rich services, tagged “linkmarks” here.