Dustin Diaz has implemented a JavaScript library on top of YUI that mimics the jQuery chained syntax. The library is called DED|Chain and has its own branded website. One thing I really like is that Dustin is packaging everything in a neat package. I think that in order to succeed with your open source projects you have to, besides offer good functionality, make a good package and brand your project, otherwise your project will drown among the thousands of others similar projects being developed.
Dustin uses Jack Slocums DomQuery for the basic functionality of chaining in DED|Chain.