I had the same question a while back, and have since found a few good places to sneak around.

• Perl6 Now, the book: A pretty good little read. It uses a Perl 5 base to explain where Perl 6 is heading; I found it to be a good start.
• Perl6 mailing lists are also a good resource, being that the language is still in development.
• CPAN's Perl6::.* modules that have been put together. There are a number of them out there now, some of which will convert P5 => P6 and vice-versa (if my memory is holding...)

I'd start there - after that you may have alredy stumbled upon others along your journies.

Good luck!

Update: I should have mentioned earlier - Perl6 Synopsys has a few good links into documents on the rules, etc. of what/where P6 has been (or is going, rather). That may be of good referece as well;)