Mendeley
A bibliography reference manager with cloud storage and BibTeX support.
Free
WebWin
Alternatives to Zotero
4 tools researchers use instead of Zotero: 1 free. Open-source and free tools come first.
SciWheel
Reference Manager to discover, read, annotate, write and share scientific research
Free plan
WebiOS
Paperpile
Reference manager made by scientists for scientists using modern technology
Paid
WebMac
Readcube/Papers
A all platform app for reference mamagement, note-taking, and more. The former Papers has been rebanded as ReadCube Papers.
Paid
WebMac
Prices and licences change, so check each tool's site. Missing one? Suggest a tool.