arXiv is now a group of Open Access repositories with e-prints or electronic pre-prints of scientific papers in the fields of Mathematics, EarthScience, AfricanScience, Biology, EngineerinScience
ResearchGate network was founded in 2008 by physicians Dr. Ijad Madisch and Dr. Sören Hofmayer, and computer scientist Horst Fickenscher. Five years later, more than 3 million researchers are already using it to present themselves and make their research visible.
Figshare launched in 2011 is an online digital repository where researchers can preserve and share their research outputs, including figures, datasets, images, and videos.
Zenodo offers an Open Access platform for all research outputs in all files and formats, and from all fields of research. Zenodo assigns each upload a DOI (Digital Object Identifier) for easy referencing and citations. Within the Zenodo platform scientific communities can create their own communities for projects, journal publications and personal repositories.
About academia.edu is a research sharing platform for academics. Next to the opportunity to share your research, Academica also applies tracking software to gage the impact of the research and the academics they follow.