The term "data sharing" can mean many different things, and in the context of medical research data is always understood to imply "secure, HIPAA-compliant data sharing".
If you are looking to meet the data sharing requirements of a journal such as PLOS-One, we recommend you either use the Stanford Digital Repository or join the Harvard Dataverse at https://thedata.harvard.edu/. For more information on the Stanford Digital Repository see https://library.stanford.edu/research/stanford-digital-repository; for more information on the Harvard Dataverse see http://thedata.org/files/thedata_new2/files/gettingstartedguidefinal.pdf.
If you are looking for something simpler, Research IT in conjunction with IRT offer a suite of tools and services to enable compliant sharing of research data, both with internal and external collaborators.
While secure email (an email with the keyword secure: in the subject line) is always an option, for large files we recommend you use a web service rather than e-mail, if only as a courtesy to your recipient, since large attachments can clutter up mail accounts.
REDCap (https://redcap.stanford.edu/) contains a tool for securely sending files to external collaborators, available from the top level tab bar. Just click on the Send-It tab to get started. If you don't see the Send-It option available, click on My Projects to get back the main menu.
Med Secure Send
IRT offers an online tool for securely sending large files to external collaborators at https://mss.stanford.edu/.
Stanford Medicine Box
Stanford Medicine has a PHI-approved instance of Box running at https://stanfordmedicine.box.com/. This online document repository is available to all faculty, staff, students and healthcare providers affiliated with Stanford Medicine. This should not be confused with the Box instance run by the University, which is not approved to store PHI.
MedWiki and MedWiki-Secure
IRT runs a Wiki for Stanford Medicine at https://medwiki.stanford.edu/. For more information see http://med.stanford.edu/irt/web/site_tools/wikis.html