Peppy is a lightning fast CSS 3 compliant selector engine with no external library dependencies. Peppy can be used along side other libraries seamlessly.
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). You can take a look for yourselves by using SlickSpeed Selectors Test and download Peppy here.
If you are designing your own JavaScript library or want to replace your existing libraries selector engine then Peppy is an ideal candidate.