Getting Involved: Revision 11
Hacking on Perl 6
Hacking on the VM (Parrot)
See the Official Parrot Wiki section on "Contributing to parrot".
Hacking on the Compiler and Related Tasks
Reading Material for Pugs Hackers
Besides these links, the Pugs distribution also provides README, READTHEM and READTOO.
General Perl 6 Tasks
A running list of tasks to work in kept in the repo at TASKS. It's a catch-all list. Something on it is bound to match your skill set!
A specific test to help with is Smart Linking.
Perl 6 Tasks for Perl 6 programmers
Preludification Candidates discusses parts of Perl 6 that can be written in Perl 6.
There's also plenty to do related to the test suite, which is written in Perl 6. See t/TASKS for work to do there.
You might also be interested to Start Your Own Perl 6 Module, or work one of the existing ones.
Hacking the Perl 6 docs
In general, offical docs are stored in docs/Perl6 and docs/Pugs in POD format, and they are fair game to improve directly. The exception is most of the documents in docs/Perl6/Spec which is the official Perl 6 specification. Improvements to the official spec should be suggested to the perl6-language list.