If you want to sell the original work, Etsy is probably the best place to start. The site is very popular and the listing fees are low.
If you want to sell prints, you could use a print on demand service. You upload your work and they create the product, in return you get a percent of the profit as commission. Redbubble and Zazzle are both reputable.
From experience, I don't recommend deviantart or ebay. Deviantart is ok for advertising commissions, but not great for selling originals and their print service will gouge you. Ebay is way too disorganized for you to get much exposure, and your listing will be buried under thousands of Chinese knockoffs.
