Diigo combines many popular link sharing features. With or without the Firefox add-on, it can highlight and clip portions of pages for retrieval and sharing. Though people can connect to each other, and to information, Diigo also connects information to information, as a byproduct of user activity. I began using Diigo to replace Ma.gnolia on word from founder Larry Halff after it suffered unrecoverable data loss.

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

Unlike most linkmarking and social media sites, to bar spam at Mahalo, humans read and approve every link and story submission.

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.

Whether some stories truly need condensing editing to 1000 characters, or suffer it tolerably, Clipmarks can excerpt and share only that, though it allows another 1000 for commentary and numerous additional pictures, each worth maybe a thousand words. In addition to viral appeal in way of a Facebook app, the new Clipcast interface looks and works like a widget, perhaps to target mobile users. For this category, a thousand character summary of a page would then seem ideal! Linkmarking, indexed from terse to featureful, might go Reddit, Del.icio.us, Digg, Google, Yahoo, MyWeb, Clipmarks, Ma.gnolia, Faves (Blue Dot), Tumblr, and Google Reader Shared items.

Oriented towards news and citizen journalism, Newsvine authors can post originals stories and seed linkmarks to stories. As a cofounder with Wired Magazine and the New York University School of Journalism, it also participates in Assignment Zero, a crowdsourced journalism experiment. Uniquely it can partition private replies, from group replies, from site-wide replies, so friends or groups can make personal and semi-private comments to your story hidden from site-wide view. It also pays authors a fraction of its ad revenue.

An amazingly full-featured and flexible photo sharing site, Flickr has become the buzz for photography on the Web. It boasts one of the most interesting collaborative filters for photography, http://flickr.com/explore/interesting/7days/ —be sure to see it. My stream includes selected works linking elsewhere.

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.