Learnboost (http://learnboost.com/) is using Node.js and is an active contributor to node projects on Github (https://github.com/learnboost).
Plurk's comet functionality is the main one people point to
http://news.ycombinator.com/item?id=1088699
Joyent also maintain a list on Github of companies using it
https://github.com/joyent/node/wiki/Projects,-Applications,-...
I don't know if it's deployed yet but Jason Roberts of techzing (Great Podcast btw, here: http://techzinglive.com/ ) has been talking about a node.js rewrite of the backend for car hire service Uber (http://www.uber.com/)
Would that that count?
Etsy is using node.js for aggregating stats: https://github.com/etsy/statsd
I know that Voxer (http://www.voxer.com) uses it and are happy with it:
http://www.theregister.co.uk/2011/03/01/the_rise_and_rise_of...
Showyou has to pull in about half a million videos a day from various social networks and that's done with Node. It makes a good web Crawler.
http://bouncely.com uses Node.js for processing Amazon SES bounce emails.
Anybots uses it to control all its robots.
I heard somewhere that Facebook uses Node for recording stats. (Can't dig up the story though :S)
http://transloadit.com/ uses node.js
Anyone know which framework the sites mentioned by the commenters use? Geddy? Express?
Since we're at it, is there any good book on node.js?
Node is in production at SimpleGeo, IIRC.
"Their"? Whose?
www.streamerapp.com is a large scale, real life node.js app now on Private beta.
Storify.com
proxlet.com - it handles millions of twitter requests each day.
Ask HN: What are the correct usages of their, there, and they're?
I have another question: Is there something that we can only do with Node.js?
Sorry for the spelling mistake. I meant there and not their. This can happen, when English is your third language (grown up in Afghanistan, living in Germany) and you don't use English every day.
Why it is not possible to edit this post/question?
Thanks also for your replies.