What lib do you use to minify and concat your static files? Possibly uglify js?
I found one called piler that seemed pretty good until i started using it. It needed a lot of patching up to get working with express 3. I got it working, but the process of getting it working makes me think that maybe this isnt a lib id want to use in prod.
We use uglify. Fast and simple and a solid node.js library.
Simple method is a 'build' target in a makefile, but you can make a whole complex asset pipeline thing if your project calls for it.
Take a look at grunt http://gruntjs.com/
You can run task-based commands with it and one of built-in commands is to minify JavaScript files (they do it via Uglify.js) https://github.com/gruntjs/grunt/blob/0.3-stable/docs/task_min.md