You need to determine whether you want to allow others to reuse your data. Before you do that, though, you need to ask yourself:
You also need to determine how you're going to share your data and make sure it's preserved for the long-term. You should have already considered using file formats for long-term access, appropriate metadata standards, and privacy and confidentiality issues with your data. Once you have determined that your data is ready to share, here are some places to find possible repositories: