Since the last question similar to this one is from 2008, I thought I'd ask it anyway to see what's new since then.
I'm looking for books or other resources (though I prefer epubs for reading them on the go) for learning how to use DTrace, preferably but not necessarily for Cocoa, ruby or node.js development.
I can really recommend this book: http://www.amazon.com/DTrace-Dynamic-Tracing-Solaris-FreeBSD/dp/0132091518/ref=sr_1_cc_1?ie=UTF8&qid=1286959740&sr=1-1-catcorr
It covers DTrace in Detail and gives you a lot of insight how to use this tool. Another great source is a Google Talk by Bryan Cantrill: http://video.google.com/videoplay?docid=-8002801113289007228
The dtrace handbook can be found here: http://wikis.sun.com/display/DTrace/Documentation
Regards, raichoo