[benzor]

If you haven't heard, patio11 is the original creator of Bingo Card Creator [1], which is both an excellent example for your purposes, and as a bonus he's helpfully shared many useful lessons from it on his blog [2].

[1] https://www.bingocardcreator.com/ [2] http://www.kalzumeus.com/greatest-hits/

[iurisilvio]

Bingo Card Creator is a great example to patio11 answer. I'll never expect someone to pay for it, but we know it worked great for him.