You never know what's going to set off a flurry of activity. Around here lately it's a thin, used paperback that Junior's dad brought home from a library sale: The Usborne Book of Secret Codes (1997). It cost all of 50 cents. Yesterday the three of us spent a good hour sending out important information, like "What would you like for dinner?," in pigpen code.
Roman numerals aren't code exactly, but are certainly intriguing to some would-be spies. (As far as I can tell, these aren't taught in elementary schools any more. Hence, the intrigue.) Agent J. has studied David A. Adler's Fun with Roman Numerals (Holiday House, 2008), copying over numbers and making notes to himself.
A printout of the Wikipedia entry on Morse code is well-used, too. I wouldn't be surprised if a homemade telegraph machine is in our future.

Susan, has Junior seen Mac Barnett and Adam Rex's Brixton Brothers books? (Well, just one book so far. But I assume it's going to be a series.) It sounds like it would be right up his alley after all those codes!
Posted by: Sarah Rettger | March 16, 2010 at 01:26 PM
Sarah. he's gotta check those out! Thanks for the tip.
Posted by: Susan (Chicken Spaghetti) | March 16, 2010 at 01:54 PM
My just received his Lego magazine, and it always includes a code to break. Which I have fun doing, even if he doesn't.
Posted by: Ian | March 23, 2010 at 07:55 AM
Ian, I didn't even know there was a Lego magazine! We should look for that. Thanks for the tip.
Posted by: Susan (Chicken Spaghetti) | March 23, 2010 at 09:05 AM
Yep, it is remarkable how inspiration can come from odd places. Another great idea sparker is digging through all the public domain books at Project Gutenberg. Some truly weird and wonderful things can be found in there -- and it's all free of copyright so those books can be quoted at will.
Posted by: Jon Bard | March 28, 2010 at 06:13 PM
Isn't it so cool that something like Project Gutenberg exists? I keep meaning to look around there more.
Posted by: Susan (Chicken Spaghetti) | March 28, 2010 at 07:52 PM