I began by finding a few programs whose construction intrigued me...
Source: Style Me Pretty
Source: Hello Tenfold via Merriment
Using the same methods I employed for both the save-the-dates and the invitations, I took my inspiration, made it my own, and designed the program in Microsoft Word. What followed (and continues to follow...) is hours of printing, cutting, punching, and assembling, but I honestly think that it's totally worth it. I think they're adorable, and (bonus!) if it's hot, they work as fans!