BibSonomy

BibSonomy is a free, web-based social bookmarking and publication-sharing system developed by the University of Kassel (Germany) in collaboration with the University of Würzburg and the L3S Research Center in Hannover.  It combines features of reference-management (for publications) and social bookmarking (for web links), allowing users to store, tag and share both academic publication entries and bookmarks. bibsonomy.org+1

Who it serves & how?
BibSonomy is aimed at researchers, students, academic groups and communities who want to organise their publication lists, collaborate on bibliographies, share links of interest, or discover what others in their field are reading. Users can tag items (publications or links) and thereby build a folksonomy—an evolving tagging vocabulary built by user behaviour. It supports exporting entries (for example in BibTeX, EndNote, HTML) so the stored data can be used in publication lists or reference management tools. Wikipedia

Key features & unique aspects

• Dual-mode: both bookmarks and publication entries can be stored and tagged. 
• Tagging/folksonomy: users assign free-form tags, which allows flexible structuring and cross-community discovery. 
• Collaborative: groups can share and explore each other’s bookmarks/publications, enhancing literature discovery across networks. 
• Export formats: Entries stored in BibTeX (for publications) and can be exported to other formats. 
• Open-source: Its source code has been published under LGPL/AGPL licences. 

Why it matters
For academic researchers, especially those working in fields with many publications and shared resources, BibSonomy offers a lightweight, networked way to manage and discover literature and links. Because it emphasises tagging and sharing, it helps surface interesting content outside one’s immediate circle.

Considerations & limitations

• The tagging system (folksonomy) is very flexible, but that also means less standardisation—tags might be inconsistent across users.
• While it supports publications and bookmarks, it is not a full-featured reference manager (like e.g., Zotero) with full integration of PDFs, nested folders, etc, so you might still need a complementary tool for more advanced workflows.
• Coverage (user activity, network size) may vary by discipline and region—some fields may have more active users than others.
• Because it is free and web-based, there is a dependency on the hosting institutions and user community for updates and longevity.
  No way to backup bookmarks