This is a list of the non-hosted social bookmarks, see here for hosted solutions.

Digg clones

• Menéame: Spanish using tags, categories, RSS links… [download]

• Pligg: Originaly based on Méneamet. With tags, plugins, templates, icons, vote buttons, language customization and advanced user profiles with gravatars, podcast support…and much more. There are a many web sites using it. See About pligg and Current Version.
• neodiario.net: NEW! Spanish, very similar to Méneamet. [license] [download]
• diggClone [download]
• Digg Clone in Ajax
• Akarru: Blogmemes engine.
• Upwarded: PHP/Ajax by Philipp Lenssen. Has a Widget for blogs. [info][download]
• Wobblog: [License][download]

Social Bookmarks

• de.lirio.us [info][download]

• FeedMarker: Ruby on Rails - Bookmark and feeds [annoucement][info][download]
• Frassle Perl Social Bookmarking and aggregator.[info][download]
• Markboo: Social bookmarks using Tags with notes, image and music support. [info][blog][download]
• Unalog Text based interface using Tags. Python [info][API][Download]
• Connotea: Perl [Download][info]
• SWIK: NEW! Nice Wiki with social bookmarking and sydicating. Info
• OpnTag: An open web-service for tagging (aka folksonomy) of web bookmarks (similar to del.icio.us), but with an emphasis on information organization, reuse and collaboration.
• Insipid: Perl - Feeds, private entries, import/export.
• LinkMeter: Perl, PHP - German with Tags and Categories.[download]
• Rubric: Perl, also powers de.lirio.us
• Scuttle: PHP [info][download]
• Feed Me Links! Social Bookmarks using Tags [download]
• Chipmark: Java/Javascript Social bookmarks using folders and labels [info][download]
• SiteBar.org: JavaScript, PHP, XSL (XSLT/XPath/XSL-FO) - Bookmark server, featuring muti-user/group access, a simple mode for the single end user, full import/export features, skinnable interface, internationalization. It integrates to sidebars of all major browsers. [download]
• Cutemarks: PHP - Little bookmark manager for public and/or private use on a Webserver with the help of PHP and MySQL. See example [download]
• Kommuni-K: C - Complete communication system with Instant messaging, Chatrooms, file sharing, Bookmark sharing, GUI to netsoul
• ol'bookmarks: PHP [screenshots][download]
• jMarks: Java - Full-blown multi-user web-based bookmark solution, written in Java. jMarks allows people to mark their online bookmarks as public or private, and can track the last time each bookmarked site was updated.
• BookmarkSync: ASP, PHP - Client/server implementation of a bookmark manager, with native integration with your favorite browsers, web-based viewing, undeletion, integrity checks, shared subscriptions, etc. Bookmarks are kept in sync across multiple computers, browsers, and OSs.
• plinks: PHP - Intended to be extremely usable in a private/group environment.
• wiklink: A very simple wiki bookmark engine. See example [download]
• Wibisa/Quicksource/QS: Rexx - Wiki-principle based intranet- and internet search assistant and bookmark sharing tool which uses auto-type detection methods, approximate (fuzzy) searches, and regular expression pattern searches to immediately redirect a user-entered shortcuts to target URIs (WIBISA). [download]
• Bookmark Sync: first goal is to create a synchronization of bookmarks in Internet Explorer. Second goal will be the creation of a GUI for composing a bookmark file from a database, and supply sharing and categorizing of bookmarks.
• Bookmark4U: Using folders. Not updated any more.
• PHP-Nuke: CMS with Social bookmark module available. [Info]
• Midgrad CMS: net.nemein.bookmarks is a bookmark manager component for MidCOM. tagging, Synchronize with a del.icio.us, Bookmarklet, xFolk-compatible output

Misc:

• Bloxor: XUL application, Open source Private RSS aggregator with bookmarks [JS/PHP/MySQL][XList][Blog][Download]

• H2O Playlist:[PR6] Open source for creating Social lists (playlists) using tags and hyperlink support (bookmarks).
  [download]
• Linkwalla: Build a list of links through a simple AJAX web interface, published via HTML and RSS. Sort of a mini-blog for links. Written in PHP5 and runs off XML files - no database needed. Includes the option to copy new links to del.icio.us and/or Magnolia. [download]
• Semanlink: Semanlink is a personal information management system based on RDF. It lets you add tags, as well as other RDF metadata, to files, bookmarks and short text notes that it allows to write. Providing a simple way to organize the tags in a graph, it allows you to incrementally define the vocabulary you use when annotating documents with metadata.
• Freetag: Tagging / Folksonomy module for PHP/MySQL applications. [API]
• PHP Tag Engine: PHP Tag Engine is a library that allows you to easily add tagging functionality to a PHP application. PHP Tag Engine has a full AJAX front-end for tagging, as well as methods for programatically adding tags in your code.
• TagFinder: NewZingo The Zingo TagFinder is a Web service that automatically extracts tags from a piece of text. The tags are chosen based on both statistical and linguistic analysis of the original text. [API]
• Taggee: scalable distributed tagging server. It features an HTTP interface making it usable from any application where tagging is needed. It can also be used as a standalone bookmark server with its HTML interface.
• Taggingmanager: a tool where each user can tag site's with RSS support. [download]
• Tasty: Tagging engine accessible entirely through a REST interface. Tasty is written in python, using the TurboGears framework.
• Bookmarks: PHP Component to manage bookmarks with Import/export capability. Can be used for links directory. [info]

API

• del.icio.us Java API
• PhpDelicious: PHP class for accessing the del.icio.us API
• Ridiculous: wrapper for del.icio.us API writing in Ruby
• pydelicious: to access the del.icio.us API from Python
• MySQLicious: a tool for mirroring your del.icio.us bookmarks into a MySQL database"
• del.icio.us API and furl.net API: API ActiveX Component for submitting to del.icio.us, furl.net, etc.
• Unoffical Digg API
• The Wiki for Finding Web Service and Open APIs
• Mozilla Bookmarks Data API Project
• For official social bookmark APIs search for the keyword 'API' here

Links:

• SourceForge.net: More Open Source Bookmarks and tools
• tegdesign.ch Bookmarks
• Del.icio.us.NET: RSS feed dll wrapper
• Delicer 0.6.0.0: del.icio.us client
• Building a simple del.icio.us clone by Jimmy O'Regan
• Web Application Development: have produced five open source applications in PHP/MySQL that emulate digg functionality.
• Taxo tools: List of taxonomy management tools on Taxo, tagsonomy wiki.
• Bookmarks Interchange Format Project [info]