Chromium is the only one I am aware of that can actually help glucose control in type 1 diabetics. If you run high more than you'd like, then it's probably worth giving a shot (no pun intended!).
I looked up vitamins and circulation on Google, and while I am not sure if the sites I saw are completely legit, vitamin E was commonly recommended. I'm a huge nut eater, so I am likely not deficient, but for those of you that aren't nutty (hehe), you may want to take E.
Vitamin D has made the news a ton lately because of its connection to autoimmune disorders. Most experts feel a deficiency in it contributes to autoimmune disorders while others feel we are deficient in vitamin D because it actually worsens the condition, but these people in the latter category (the Marshall protocol variety) are in the minority - most feel we need more D because the deficiency is actually a problem, not the result of some other kind of problem.
Finally, I've never heard anything about cinnamon and diabetes, or that it was even in vitamin form. :) I guess I'll have to look that one up sometime.
EDIT - just read further - for those who are worried about OD'ing, be especially wary with fat-soluble vitamins. It's harder to OD on water-soluble ones, but even then, moderation is key, of course. As for chromium being a metal, most of the minerals our body needs are somewhat metallic (iron, anyone?), but we only take or eat them in small amounts anyway, so I wouldn't worry too much if you have a metal allergy.