I know someone who is doing some work on the Trinity from a philosophical point of view, and he's currently running a survey about Trinitarian belief. You do have to register, but it's a fun quiz for those who like theology, and you get the results of everyone who's taken it at the end. He's trying to learn what Christians think about the Trinity, so it's primarily for those who do consider themselves Christians. He's particularly interested in targeting seminary students or others who study theology of some sort. If you can help spread the word to seminarians or other students of theology, he would greatly appreciate it.
To pass the word around, I think I will link this survey on the trinity too.