Some federal agencies, as part of their grant requirements, may require researchers to share their data. Placing it in a repository will ensure that it is preserved and publicly accessible. Publishers also may have requirements for making data associated with an article available. Be sure to check for this information before submitting an article to a journal.
Repositories can be a stable place to store and share your data. Data sharing is also now a requirement for many granting agencies and journal publishers. Below are some guides to what options are available by discipline.