Stop all the downloadin'! It turns out that Nintendo had those "downloadable" Professor Layton puzzles on the cartridge all along! When you download a puzzle, all you're downloading is an unlock code. Which isn't a big deal -- it's not like you're paying for the extra content or anything.
One user figured out how to find that content in the game data, and has compiled all 162(!)
bonus puzzles, with screenshots, on a single web page. The solutions are also provided, but hidden behind links so you can actually play these puzzles if you want. Or you can spoil a friend's good time every week as you wait patiently for him or her to complete the download and then blurt out the solution.
[Update: this is actually all the puzzles!]