I did this as a fundraiser for the writing conference I put on this summer–I thought "Cats! Writers! They go together like cats and librarians!" so I put it on some mugs n' stuff at CafePress, and sold…exactly none (I bought some mugs to give away, but that doesn't count). Of course, selling through CafePress means you don't get any impulse shoppers, but we didn't have money to invest in merch.
The evaluations from the conference came in this week, and the comments–oy. The conference was overpriced, the presenters were unprepared, I was unfriendly, there was too much white bread and starch in the meals…the numbers were okay, though, 90% responses "good" or "very good", so…there.