There's Perl6::Perl5::Differences, which is (apart from the section on POD) up to date.

It's a bit longer than a typical cheat sheet, though.

I've also written a blog that introduces Perl 5 programmers to Perl 6, and showcases some cool features (and occasionally I update it).

(Update: TimToady removed the section on POD, so it's not out of date anymore. I thought about doing that myself, but didn't have the guts to.)