I'm pleased to announce that Ruby Cross Reference has just been rolled 
 out.

   http://rxr.whitequark.org/

 Have you ever wanted to know what exactly VALUE is? Wondered about 
 rb_str_new2
 implementation? Tried to grep some obscure function? If your answer is 
 yes,
 then RXR is for you!

 Grep is from stone age. The Cross Reference, a tool which originally 
 was written
 to index Linux kernel sources, will instantly find declaration and all 
 references
 to an identifier, converts tokens in source file to convenient links 
 and even
 has some full-text search capabilities.

 Three versions of Ruby source tree are indexed: 1.8.7, 1.9.2 and HEAD, 
 all taken
 from Ruby mirror on GitHub and updated daily.

-- 
   WBR, Peter Zotov.