A list of well known companies using Redis:
<a href="http://www.infoq.com/presentations/Real-Time-Delivery-Twitter">Twitter</a>
<a href="https://github.com/blog/530-how-we-made-github-fast">GitHub</a>
<a href="http://www.xdata.me/?p=353">Weibo</a>
<a href="http://engineering.pinterest.com/post/55272557617/building-a-follower-model-from-scratch">Pinterest</a>
<a href="https://twitter.com/robustcloud/status/448503100056535040">Snapchat</a>
<a href="http://blog.zawodny.com/2011/02/26/redis-sharding-at-craigslist/">Craigslist</a>
<a href="http://nosql.mypopescu.com/post/3342598062/redis-at-digg-story-view-counts">Digg</a>
<a href="http://meta.stackoverflow.com/questions/69164/does-stackoverflow-use-caching-and-if-so-how/69172">StackOverflow</a>
<a href="http://code.flickr.com/blog/2011/10/11/talk-real-time-updates-on-the-cheap-for-fun-and-profit/">Flickr</a>
And many others!, techstacks.io maintains a list of popular sites using Redis, the information may not be always updated since many companies change their tech stack during their lifetime, but is an interesting resource. link policy: we only link major sites, we used to also link to small companies and services but this rapidly became impossible to maintain.