If you use the ECC "H" for Best and 10 for the size you can hold aproximately 7,000 characters.
I don't think people have really used these codes to their fullest extent yet. Lots of business card applications but you could use them as the basis for an adventure game.
Also great for scavenger hunts with a group of folks.
If you want some real interesting background on the code read about the code behind the code "Reed Solomon" error Correction codes. I do not fully understand the math but it is pretty fascinating.