Quick Summary:
We just open-sourced the asset packager that powers the DocumentCloud prototype. It does the asset concatenation and (YUI) compression that you'd expect, as well as ahead-of-time gzipping, built-in support for JavaScript templates, and automatic Data-URI/MHTML image embedding.
Quick Links: Project Page: http://documentcloud.github.com/jammit/ Source Code: http://github.com/documentcloud/jammit Image Embedding Example: http://jashkenas.s3.amazonaws.com/misc/jammit_example/normal.html
We'd love to expand the gem beyond just Rails, although it's a bit out of scope for us. Patches to add Sinatra support, for example, will be warmly welcomed.