This article explores the Public-Resource Computing concept, an idea that has been successfully developed in the scientific community a few years ago, which involves the use of spare computational resources available in the millions of PCs in the world connected to Internet. We discuss the SETI@home project, the most successful example of this concept, and we describe the BOINC (Berkeley Open Infrastructure for Network Computing) platform, a software system created to make it easy for scientist to create and operate public-resource computing projects.