This morning I spoke to high school students attending portfolio day at Friends University. I suggested to the students that, while a physical portfolio is essential, an online portfolio can be a useful way to leverage the work and help develop an online reputation. Useful when someone needs to see your portfolio right now, or when your portfolio needs to be in two places at once. Saves on postage, too.
Etsy.com, online marketplace for selling handmade things.
Issuu.com, tool for presenting and sharing formatted printed documents online.
VisualCV.com, currently in beta, allows you to create an interactive, online CV and post it in a searchable database.
DeviantArt.com, suggested by a student. International art community that allows you to upload your art, view art by category and participate in social activities.