I'm currently offering prints of my pictures in the following three online stores:
DeviantArt Prints - Extremely high quality, range of sizes 4x6" prints to 30x40" posters, and four print types: glossy, matte, lustre and canvas + cards, magnets and 252-piece puzzles.
ImageKind - High quality framed prints.
Zazzle Prints - Prints, cards, mugs, apparel and stamps.
Prickie.com - Button badges.
My CafePress Main Store - Prints, buttons, magnets, mugs, mousepads, pillows, coasters, cards, apparel and stamps. If you want more stuff of some specific picture, here are links to "substores" titled by pictures they contain mainly.