Just this morning we noted that Apple had not yet come out with a tool to kill the Flashback malware, and that Kaspersky and F-Secure had both developed their own free tools. This afternoon, Apple released Java for OS X 2012-003 to remove "most common variants of the Flashback malware."
According to the update notes, the Java web plug-in is also configured to disable the automatic execution of Java applets -- that's another way to keep malware like Flashback from spreading. Apple says that "This update is recommended for all Mac users with Java installed."
Note that the link about the update was not live at the time of publication, but was listed as http://support.apple.com/kb/HT5242. You can get the update directly from Software Update.