Organized as a snippets repository in matrix form (ok, let's put 'table' for 'matrix') it could conveniently display snippets in a target language that serve as an analogue of functions of a source language. For example, PHP function string file_get_contents($filename) is presented in Python as a :
f = open(filename)
r = f.read( )
Hovering the PHP API function name could popup a small DHTLM window with function description and a link to official documentation. Main link outside the popup area leads to user content. The resource is a collaborative area that reflects the state of language mappings between different language APIs, allows users to submit their own versions, vote, comment, refactor comments and narrow the scope of original API. It could also allow to work out and point best practices of using languages in specific areas.
I do not know of any resource like this one yet.