Zotero (https://web.archive.org/web/20150906100323/http://www.zotero.org/?) is a reference manager built as an extension of the Firefox (https://web.archive.org/web/20150906100323/http://www.mozilla-europe.org/en/firefox/?) web browser. The best introduction to Zotero is probably this short video.
Last week the newest version (1.5 beta) was announced (https://web.archive.org/web/20150906100323/http://www.zotero.org/blog/zotero-15-beta-released-join-us-in-the-clouds/?) on the Zotero blog. Among the most exciting new features is the synchronization of library data with the Zotero server, which in the future will allow a lot of interesting social features. I asked Trevor Owens from Zotero a few questions about Zotero, particularly some of the new features.
Zotero is an easy-to-use yet powerful research tool that helps you gather, organize, and analyze sources (citations, full texts, web pages, images, and other objects), and lets you share the results of your research in a variety of ways. An extension to the popular open-source web browser Firefox, Zotero includes the best parts of older reference manager software — the ability to store author, title, and publication fields and to export that information as formatted references — and the best parts of modern software and web applications (like iTunes and del.icio.us (https://web.archive.org/web/20150906100323/http://www.delicious.com/?)), such as the ability to interact, tag, and search in advanced ways. Zotero integrates tightly with online resources; it can sense when users are viewing a book, article, or other object on the web, and on most major research and library sites it will find and automatically save the full reference information for the item. Since it lives in the web browser, it can effortlessly transmit information to, and receive information from, other web services and applications; since it runs on one's personal computer, it can also communicate with software running there (such as Microsoft Word). And it can be used offline as well (e.g., on a plane, in an archive without WiFi).
For most researchers the web is the first and primary point of entry for their research process. We thought it would be ideal to integrate Zotero as tightly as possible with the interface researchers already use to interact with the the journals, libraries, and databases they regularly consult.
Two reasons, first as a extension Zotero can sit alongside any page a researcher visits. Many of our users will keep Zotero partway open as they work on research online, allowing them to organize and annotate their research without leaving the page they are on. Second, as an extension users have full access to their collections when they are offline. This is particularly important for researchers working in remote locations or with flakey connections. For example, researchers working in offline archives can manually add items and attach scans and photos. If you're writing a paper on a plane you can add citations to your documents. In short being inside the browser gives us the best of both worlds. Zotero offers direct connectivity to web content, while still always remaining accessible. The last thing I would note is that Zotero is rapidly becoming a web application. With our newest release users can browse and share their collections online and in the near future users will be able to further manipulate their collections through our web application.
Both Google Gears (https://web.archive.org/web/20150906100323/http://gears.google.com/?) and Zotero rely on a local instance of sqlite (https://web.archive.org/web/20150906100323/http://www.sqlite.org/about.html?) for data storage, but Zotero predates Gears by over a year. Google Gears is intended more to synchronize a web application for offline use, while Zotero fundamentally is a research database that users expect to be able to interact with fully regardless of their network connectivity.
Yes, users can drag and drop citations and bibliographic entries into google documents, or for that matter any sort of text field. We have a short screencast (https://web.archive.org/web/20150906100323/http://www.zotero.org/support/zotero_and_google_tools?) which demos this functionality.
CSL (https://web.archive.org/web/20150906100323/http://www.zotero.org/support/dev/creating_citation_styles?) is an XML language for citation formatting. It is designed to provide a nice balance between power and ease-of-use. It is also designed to be independent of any particular application, document format, or programming language.
At the moment users can export collections and libraries and email them to associates. Users can also share their library online, and by next week users will be able to import references directly from any users shared library. By next month users will be able to create groups for more seamless sharing of references and attachments.
In many ways the collaborative features currently in the works for Zotero are similar to the other services you mention. I think the biggest difference is the way in which sharing collections through groups will be tightly coupled into the Zotero client, and writing applications through our Word and Open Office plugins. The social and collaborative features we are launching directly connect into our hundreds of thousands of users' existing workflows. Zotero is also a non-commercial, open-source project directed by academics who are committed to enabling scholarship. Finally, Zotero is oriented toward storing anything related to your research (papers, books, audio, video, datasets, images, etc) while other solutions are almost entirely oriented toward working with research papers.
Over the last two years as the community lead and evangelist I have been responsible for spreading the word about Zotero through workshops and presentations at conferences and institutions, as well as helping support the ever growing community of users, evangelists, and developers through Zotero's forums and by writing a majority of Zotero's user documentation.
Before working on Zotero I worked as the press coordinator for the Games Learning and Society Conference in Madison and as a Academic Advisor at the University of Wisconsin. My undergraduate degree is in the History of Science.
You can consult our development roadmap online here (https://web.archive.org/web/20150906100323/http://www.zotero.org/support/development_roadmap?). Beyond that I would recommend taking a look at the work we are doing with the internet archive here (https://web.archive.org/web/20150906100323/http://www.dancohen.org/2007/12/12/zotero-and-the-internet-archive-join-forces/?). Once you take a look at those I would be happy to answer any questions (https://web.archive.org/web/20150906100323/http://www.zotero.org/support/contact_us?) that come up.