Node Knockout was a hell of a lot of fun. Joyent should get mad props for opening up their space like they did (and if you were in the crowd who couldn't make it, try to do so next time, provided they do it again - totally worth it!).
My team and I made http://nodeknockout.com/teams/anansi, which was pretty fun to work on. Actually gave me a lot of material for some writing, because there's quite a bit of hackery we ended up doing behind the scenes to get it to work properly. Extremely fun to push new tech like this.
It's not really furnished to best, but worth checking out, a Hacker News Reader http://nko-naughtify.heroku.com/reader. Appreciate the attention. Really sorry for self promotion :)
I've learned a lot and loved the opportunity to have an excuse to gather my brother and friends from other nearby cities in my apartment for coding and hack on ideas that fills my archive of notes-that-wont-see-the-light-of-day…
Our entry is this one http://umeboshi-fireteam.no.de a communication server to be used by web-apps (and webpage) developers that want to distribute the UI control elements over multiple (mobile) devices. Make sure you check out the examples :)
It was a ton of fun and a great chance to learn about node.js.
My team made a simple file sharing application, http://nodeknockout.com/teams/done-js. Our app does not host the upload, it merely connects the sharer to clients over HTTP.
My team and I made http://nodeknockout.com/teams/anansi, which was pretty fun to work on. Actually gave me a lot of material for some writing, because there's quite a bit of hackery we ended up doing behind the scenes to get it to work properly. Extremely fun to push new tech like this.