<p>I guess it depends on what you mean by "X".  If the question is, 'where can I get data on US state-by-state unemployment rates?' (answer: <a href="http://research.stlouisfed.org/fred2/release?rid=112&amp;ob=u&amp;od=asc&amp;filter%5B0%5D=&amp;filter%5B1%5D=" rel="nofollow noreferrer">FRED</a>), then I don't think it belongs here just as was decided previously in the question @whuber links.  I further agree with @Procrastinator that the proposed data Q&amp;A site is a good idea for stuff like that where someone is looking for a <em>particular</em> public data set, but is having trouble finding it.  </p>

<p>However, there could be a different version of this question that I think <em>could</em> be worthwhile for CV.  Specifically, I have often thought of asking a CW question to have a place where links for statistical data sets of different kinds for demonstrating statistical properties or practicing different kinds of analyses could be listed (an example link would be to <a href="http://lib.stat.cmu.edu/DASL/" rel="nofollow noreferrer">DASL</a>).  The idea is that it would serve as a recourse similar to <a href="http://rads.stackoverflow.com/amzn/click/0412399202" rel="nofollow noreferrer">A Handbook of Small Data Sets</a>.  We <a href="https://stats.stackexchange.com/questions/138/resources-for-learning-r">have</a> such a repository of links to resources for learning R, for example, and <a href="https://stats.stackexchange.com/questions/12670/data-apis-feeds-available-as-packages-in-r">one</a> for R packages that can read data from feeds.  My idea would be analogous to those, but I've never asked because I've never been sure it it's really appropriate.  </p>

<p>If this is what @Dimitriy means, then I do think there could be real value in such a thing, although I recognize that the community is ambivalent on this type of stuff.  For what it's worth, we do have <a href="https://stats.stackexchange.com/questions/16130/datasets-for-data-visualization-examples-teaching-and-research">this</a>, which is also similar but more focused and doesn't have the open-ended 'big-list' quality to it.  </p>

<p><strong>Update:</strong> I don't know how I had missed it, but it turns out we do have something like this: <a href="https://stats.stackexchange.com/questions/7/locating-freely-available-data-samples">Locating freely available data samples</a>.</p>
