The Body Shop sells a great vitamin C skin care line and it's reasonably priced. I've also tried SkinMedica's Vitamin C complex and I like it. It's pretty pricey though.
Ive used PureDeming Intense Gel for some time now and love the stuff. Deming also has a "fresh pack" vitamin C serum that I've not tried yet but I'm sure it's fab...all her other stuff is.
I use Juice Beauty Antioxidant Serum, but I'm also looking into the Murad Essential-C Daily Renewal Complex and Boscia Antioxidant Recovery Treatment C.
I use any of the Skinceuticals vitamin c serums. It's expensive buying retail, but I like buying the sample vials (6 vials to a pack) on eBay. The vials stay fresher than the full size bottle. Each 6 pack is about $15 and lasts about 3 months.
I use celex c serum, also aloette has one, powder form that you can mix with your moisterizer, it's pretty good, make your face look very healthy. good luck