Matt sez, "This site's purpose is to raise awareness of MD5's prevalence in most applications of cryptography (SSL, digital signatures, IDS software) and it's inherent weaknesses. MD5CRK is a distributed computing project that seeks to find a collision in the MD5 hash algorithm — a property that hash algorithms are not supposed to have. The part of this project that has proved controversial is the (optional) use of an applet-based client. You put the applet on your site and your visitors contribute CPU cycles whether they notice or not."
(Thanks, Matt!)