Zotero is "the only research tool that automatically senses content in your web
browser, allowing you to add it to your personal library with a single click."
"Zotero collects all your research in a single, searchable interface."
After reading The Gilded Hour by Sara Donati (aka Rosina Lippi) I visited her web pages, where she recommends Zotero. Zotero is free, open source and just what I need. It is what every genealogist, student, political activist and writer needs.