Before I read all the rest of the replies, I just want to say that I have been going with the idea of getting both Ascorbic Acid AND Sodium Ascorbate in my Vitamin C pills.
I think the Vit C. producers are being negligent in not allways having both, getting both was recomended to me 25 years ago.
Also, when possible, avoid the bad fillers and so on, even the stuff that holds it together. All that can be made from "vegatable sources" if they care to do it.
I hate to be "branded" by going with a corporate name, but the Jamieson "Citris Juice" which I have right here in my hand and in my mouth, is the one that fits the conditions mentioned above.