Scan your art piece if it's not too large. You can photograph bigger pieces, or take it to a local printer who will have the capability to scan larger pieces. Save the scanned work on a disc in high-quality JPEG format.
Find a printing company such as Kinkos or an office supply store like Staples. These places offer options for printing your art in different sizes and with finishes such as matte and gloss. They can frame the art for you as well. If you have a local hobby shop, check to see if they offer framing services.
Consider an online print-on-demand service. These services allow you to upload your work and design your art prints using built-in design tools (see Resources). Besides standard prints, you can have your art work put on shirts and other items.