AP Physics reader Craig Fletcher made me aware of learnapphysics.com, a site run by his colleague Richard White at the Polytechnic School in Pasadena. [No, not Cal Tech, an independent high school near Cal Tech where many professors' offspring attend.] Richard provides -- for free -- an new AP physics-style multiple choice problem each day. He'll even deliver his problem automatically to your email inbox. Richard bills his service as a study aid, but I think of it just as much as a teacher's aid. Need a multiple choice question quickly for today's quiz? Look at his site.
I browsed a bit, and while I can't vouch for every question, everything looked quite strong -- at the correct level, doable without a calculator, with reasonable language. The only caveat I'd attach right now is that physics B and C questions are mixed together. Nothing wrong with that at all, just be aware. Generally multiple choice questions from unedited sources are buyer-beware. I don't recommend using questions from the ubiquitously available College Physics tests you can find online, for example. But Richard's site seems like one I can recommend.
It's not like there's any real shortage of good AP-style problems out in the online universe. But, any further suggestions, please send them along, and I'll point readers in that direction.