James Donaghue has released Peppy, the first release of his CSS 3 compliant selector engine that runs independent of one particular library (and can thus be used with any of them).

He has some bold claims on speed:

As it stands now Peppy is faster¹ than all other major JavaScript libraries with DOM querying capabilities (Prototype 1.6.0.3, JQuery 1.2.6, MooTools 1.2.1, EXT 2.2, DoJo 1.2.0, YUI 2.6.0). It is faster² than Sizzle by John Resig and it also is cross browser (IE included). Take a look for yourselves, I have a profiling page set up here.

At 10k it is an ideal replacement for other excellent but bulkier libraries (whose feature sets span beyond DOM querying) when features additional to DOM querying are not needed in your web application. If you are designing your own JavaScript library or want to replace your existing libraries selector engine then Peppy is an ideal candidate.

Comments, both positive and negative, are most welcomed and desired. I want to improve this thing! Please take a look here.

John Resig has also discussed a new selector engine that he is working on that is performing very well, and there has been much talk about having engines that can be shared resources for the Ajax libraries.