Although you can share data just by posting it on your website, by using a trusted or even certified repository, you will make your data discoverable and citeable. There are general and domain-specific repositories. A few common ones are listed below:
Note: Not all of the repositories listed can ensure long-term preservation of your data; contact each one for more details. For a more repositories, see on of the resources on the right.
The above is only a partial list of data repositories, If you are interested in other options, the Open Access Directory maintains an extensive list of repositories.