For the longest time, 64 bit versions of the Java Runtime Environment (JRE) and Java Development Kit (JDK) have not included a Java Plugin.
This fact has let us 64 bit Linux users out in the cold when it comes to running Java applets in our operating system of choice. There are workarounds, but they involved downloading a 32 bit browser and a 32 bit JRE, a less than ideal solution.
There has been a bug in Java's bug parade reporting this issue (submitted in 2003!), finally, today I got notice that this issue will finally be addressed.
According to the comments in the bug report, JRE 6u12 will include a Java plugin for 64 bit Linux, freeing us from jumping through hoops to be able to execute Java applets under 64 bit Linux.
JRE 6u12 is scheduled to be released early 2009.