Perl 6 implementations: Revision 1
Unlike previous versions of Perl, where the translator actually defined the language, for Perl 6 the language is defined by its specification (the synopses). Thus, there are several implementations of Perl 6, and none of them are designated as "The Official Perl". As Synopsis 1 indicates, Perl 6 is anything that passes the official test suite.
Here's a brief synopsis of the current implementations. View their individual pages for more details.
As of this writing (2007-12-28), Pugs is the most complete of the available implementations, but its development seems to have stalled somewhat. Pugs is written in Haskell and currently hosts the official Perl 6 test suite.
Parrot is a virtual machine for dynamic languages, and was the original target for Perl 6. The perl6 on Parrot compiler is undergoing rapid development at the moment.
(information needed here)
Not Quite Perl (NQP)
"Not Quite Perl" (NQP) is not really a Perl 6 implementation, even though it uses Perl 6 syntax. NQP is a tool to help write compilers and libraries for Parrot, and is not really intended as a complete end-user programming language. It uses only limited forms of Perl 6 syntax, and provides only native Parrot runtime support (i.e., no specialized Perl 6 libraries or functions).