For the last two years, I’ve ordered the Nimble Pros Software Craftsmanship calendars, which use ‘motivational poster’ style pictures to depict various software practices and principles worth keeping in mind. Here’s one of the walls at work, where I’ve got the calendars cut up and displayed for easy reference:

I like being able to point to a principle when its use pops up, and they provide a nice illustration of things everyone should be aware of.