The Catalyst::Engine standalone rewrite is called Isotope, and although it's being worked on, the author is apparently somewhat famous for not commiting very often.
Some time early in the new year, I'm going be (hopefully) helping to get Isotope $done, so I can replace the engine-layer of my own web application system with it.
With you and I and a few others, I reckon we should be able to push it through to completion reasonably promptly. What do you say? :)
Which sounds really nifty, but I have to get this done now. I already have a basic implementation (pretty specific for our needs). I like the thought of Isotope, but I need to get my core needs done and move on :/