Hosting everything on Linode.
nginx as a load balancer (running 4 node processes on different ports as upstart scripts with respawn) and for serving static files.
Express + Jade (but I do most of the things on the client - calling REST API)
redis as a session store: https://github.com/visionmedia/connect-redis
DB - MongoDb (I also use Mongoose: http://mongoosejs.com/)
I also host most of the static resources on S3 and they are served through CloudFront CDN.
At first I used this module (for easier deploying the resources to S3):
https://github.com/niftylettuce/express-cdn
but later I had to rewrite most of the things to handle my specific requirements (using knox).
Tests (client and server side): Mocha + sinon + chai
CSS: Less + less-middleware
JS: UglifyJS + express-uglify
I'm also running a worker process and a scheduler process. For communication between the worker, web and scheduler processes - RabbitMQ.
Deploying everything with git push in master (custom github post push hook).
No build server. Have nothing to build.
Client side: jQuery (of course) + AngularJS + custom code for bootstrapping the SPA.
KnockoutJS - Naaw.
Hope this info helps.
P.S. Authentication: http://passportjs.org/