There are a variety of good vegan supplements.
Dr. Furhman's "Gentle Care" is a multi-vitamin designed for a vegan diet (check it out at www.drfuhrman.com
carries a variety of vegan supplements.
In addition to what one usually considers as supplements (pills or liquids that contain a combination of isolated vitamiins and minerals), there are also whole-foods based supplements (sometimes refered to as "superfoods.") They are what I prefer, and include green supplements (like Vitamineral Green, which you can check out at Vegan Essentials), açai, maca, goji berries, etc.
One important vegan supplement is B-12. I prefer the Pure Advantage B-12 spray that VE sells, both for convenience, and because it contains methylcobalamin (rather than the cyanacobalamin that is the form of B-12 one usually finds in supplements) which is more easily/directly assimilated by the body.