Academia.edu - Academia is a website where you can share papers that are written with other users. You can use a Google or Facebook account to sign in to the website.
ResearchGate - Access scientific knowledge, and make your research visible
Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.
BioSeek Mobile - BioSeek Mobile - Next Generation Search For Life Sciences. Fast. Efficient. Free. We process at one go multi-component searches that are normally quite time consuming. We strive to deliver the clearest representations of massive amounts of data.
Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
The Literature Network - We offer searchable online literature for the student, educator, or enthusiast.