The royal college of art has an wonderful site featuring the RCA secret project which is a collection of 2500 postcards created by leading international artists as well as current students. The secret is that we don't know which artist created which piece of art. The project is a fundraiser (that you had to sign up for long before I discovered the project) with each piece costing 35 pounds, regardless. It's a great adventure to go through the many, many small pieces of art created on the same sized postcard. Plus you can set up a personal favorites page to capture the ones you like best in one place. Here are my 55 fav's from the 2500.