What are the most useful JSF tag libraries?
Initially, I'd like one recommendation per answer, if you also use that library then just vote up the previous answer.
My goal is to get to know what's out there apart from the most obvious ones:
xmlns:h = http://java.sun.com/jsf/html
xmlns:f = http://java.sun.com/jsf/core
xmlns:ui = http://java.sun.com/jsf/facelets
These three are basically the only ones I know! :-o