For artists

Anyway, tips for artists...

Print on demand and drop-shipping

Add it to your website. Sell prints without having to print and ship them yourself.

Full service online galleries

They do all the work. You just upload your photos. However, they either get a much higher commission, or you have to pay a monthly membership fee.
fineartamerica.com - very easy. Everyone is approved. Just upload your art and set your markup
artstorefronts.com - make your own ecommerce art store - with automated print fulfilment