The Berkeley Open Infrastructure for Network Computing (BOINC) is an open-source platform that enables researchers to run distributed computing projects on thousands of public PCs. BOINC was developed by the team behind SETI@home, the screensaver programme that analyses radioastronomical data for signs of extraterrestrial intelligence, which has been downloaded on more than 5 million computers. Since BOINC's launch two years ago, several scientific projects have implemented it, attracting thousands of 'PC volunteers', CERN's LHC@home project being one of these. This seminar will review two of these projects, both from the point of view of the scientific computing challenges they involve, and the scientific results they aim to produce. The seminar is in two parts: